Abstract: The effects of light and thermal and the hydrolysis of bis(triphenyl-silyl)chromate and the surface reactions in the preparing process of bis (triphenylsilyl)chromate catalyst have been studied. The results show that while the bis(triphenylsilyl)chromate was precipitated on the silica, it was reacted with hydroxyl group of surface of silica, and formed a surface organo-chromium compound, but the valent state of chromium was unchanged. After added triisobutyl aluminium, the surface compounds were reduced to form low-valence surface organo-chromium compounds which contained Cr-Cor Cr-Obond. There was catalytic activity for olefins polymerization. The load mechanism of active component of this catalyst system has also been discussed.