Abstract: The seeds of Pinus tabuliformis were cultivated at (25±1) ℃ and the mechanism of endogenous hormone of endosperm during initial germinating stage was discussed by measuring the changes of GA3, IAA, ZR and ABA contents. The results showed that the contents of endogenous hormone changed differently during initial germinating stage. The content of GA3 did not change obviously during the first 27 hours of cultivation and increased afterwards to the peak value with 18.87 ng/g at 72nd hour. But those of IAA and ZR increased at first and then decreased. The content of ZR changed a little in the first 9 hours of cultivation and increased afterwards to the peak value with 15.57 ng/g at 45th hour，and then decreased. The IAA content during the first 18 hours was basically stable ranged from 22.22 to 22.54 ng/g and increased rapidly afterwards to the maximum value with 29.06 ng/g at 54th hour，and decreased afterwards. The content of ABA did not change greatly during the first 18 hours of cultivation and decreased rapidly afterwards to the lowest level at 72nd hour (40.10 ng/g). The ratios of GA/ABA，ZR/ABA and IAA/ABA changed a little in the early stage and increased afterwards to the peak value at 72nd hour. The changes of endogenous hormone of endosperm were consistent with seed germination.