Abstract: 12carboxy8hydroxy 7,8dihydroabietic acid (5a) and its methyl ester (5b) was prepared through several steps, including acidification, isomerization and esterification, of 2amino2methyl1propanol salt of levopimaric acid transannular peroxide, which was obtained from directly photosensitized oxidation reaction of 2amino2methyl1propanol salt of levopimaric acid isolated from pine oleoresin. The reaction of 5a and 5b with 2,4dinitrophenyl hydrazine were investigated, and then the products were characterized by means of UV, IR, 1H NMR, 13C NMR, and elemental analysis. The experimental results showed that the new compounds 12(2,4dinitrophenylhydrazono)8hydroxy7,8dihydroabietic acid (6a) and its methyl ester (6b)，which have an extensive π electron conjugation and structural stability, were synthesized by a condensation reaction of 5a and 5b with 2,4dinitrophenyl hydrazine by using concentrated sulfuric acid as catalyst.