Smith translated thousands of English words from about 80 hieroglyphs. Joseph said this was the writing of Abraham and the word of his god. Actually it was a variant of the Book of the Dead, a pagan Egyptian magic book filled with heathen idols, often buried with mummies. Dr. Richard Parker of Brown University in a personal letter to Marvin Cowen dated Jan. 9 1968 said, "I have seen Joseph Smith's Egyptian Alphabet and Grammar. The interpretation of the signs purported to be Egyptian have no resemblance to the meaning ascribed to them by Egyptologists." Dr. A.B. Mercer said 50 years ago, "Any pupil of mine who would show such absolute ignorance of Egyptian as Smith does, could not possibly expect to get more than zero in an examination in Egyptology." (Improvement Era, v.16, p.615.). Dr. John A. Wilson wrote, "...as far as I am concerned I see pieces of two or possibly three different papyrii and every one of them looks like a traditional Book of the Dead." (letter Jan. 5, 1968.) http://www.biblequery.org/OtherBeliefs/Mormonism/BookOfAbraham.htm

SHORT ANSWER: He didn't translate anything. It was a blatant con that has been discredited time after time after time by Egyptologists (as documented in Alatea's answer). LONG ANSWER: Well there's a real problem here that Mormon Critic John T. has summarized nicely - though a bit more polemically than I normally like. (however, the content is excellent despite the polemic tone) "The History of the Church, Vol.2, Ch.17, p.238 indicates that Joseph Smith devoted the rest of the month of July to his work: "The remainder of this month, I was continually engaged in translating an alphabet to the Book of Abraham, and arranging a grammar of the Egyptian language as practiced by the ancients." Also in October 1835 History of the Church, Vol.2, Ch.21, p.286: "This afternoon I labored on the Egyptian alphabet, in company with Brothers Oliver Cowdery and W. W. Phelps, and during the research, the principles of astronomy as understood by Father Abraham and the ancients unfolded to our understanding, the particulars of which will appear hereafter." Like Haman on his own gallows, Smith hoisted himself upon his own instrument of destruction in a most inglorious way, hence the petard is a most apt description of what he did. Twice he uses the highly inaccurate term, "Egyptian alphabet". There is no such thing in reading ancient Egyptian. In grammar school, we ALL learned the proper name for early Egyptian writing: Hieroglyphics. Hieroglyphics is a form of writing that makes pictures instead of words, thus hieroglyphics are also considered as pictographic writing. Once one knows what the pictures represent, it is relatively easy to decipher a meaning in a scene. This god is doing that to someone who did something nasty as a form of retribution in the afterlife, etc. In reconstructing that, there is no way that moderns can learn the language that the ancient Egyptians spoke. That is because we have no way of reconstructing the phomenes, the basic building blocks of a language that distinguish in English the differences between red and bed. To do that, and others, it requires an alphabet. But the problem is that hieroglyphics is a NON-ALPHABETIC form of writing because it is a PICTOGRAPHIC form of writing. Because hieroglyphics is pictorial, it is non alphabetic. Therefore there is no extant alphabet. Therefore Smith lied about that. Because there is no ancient Egyptian alphabet, there are no building blocks of language of any sort. Therefore there are no phomemes. representing sounds Therefore there are no words. Since there are no words, there are no nouns, verbs, etc Since grammar is the study of the relationship of words to other words. Therefore Smith also lied about constructing a grammar. Because there are no words, but merely pictures, Smith needed to know the meanings of each of the figures in the hieroglyphs to accurately translate them, and he did not, for each god of Egypt was depicted differently from others, but the differences were consistent. For example one god always has a human head, and another one always has the head of a raven, etc. I could go on and on about the implications of this, but the point is well established: SMITH WAS A LIAR AND A FRAUD" http://www.concernedchristians.com/index.php?option=com_fireboard&Itemid=42&func=view&id=80102&catid=3#80102