It was investigated by ToF-SIMS（Time of Fright secondary ion mass spectroscopy）for the steelsurface after treated with 1mass％ 3-Gricidoxypropyltrimethoxysilane（GPS）aqueous solution anddried. The mass of the observed fragmentation from the siloxane structure caused by GPS increasedwith the time after solution mixture. It is thought that this phenomena was caused by condensationof GPS in aqueous solution, and in especially, it was observed for the higher mass fragmentation after48hours or more. The fragmentation caused by the bonding between steel surface and GPS molecular（Fe-O-Si）was observed to decrease remarkably 48hours or more. It was thought that higher massof GPS by condensation in aqueous solution prevented the adsorption of GPS on steel and the nemberof bonding between GPS and steel surface were decreased.