Objective: To study the effect of surface configuration and roughness on the corrosion resis tance of pure Titanium (Ti) after used in oral environment for half a year. Methods :Three edentulous volunteers with healthy oral mucosa participated in an in vivo study. Four kinds of pure Ti testing pieces with different surface roughness were fixed in the polished surface of upper complete dentures and the other in the tissue surface of the dentures. After 6-month wearing the denture, dynamic polarization curves were traced with electrochemical method. Results :Ep and Ip of specimen used in oral cavity was higher than that left in air,which meant corrosion resistance falling. Compared to plane one,Ecorr of wrinkly specimen was more positive,and Ep and Ip were more higher,so its corrosion resistance reduced. With the increase of surface roughness,Ep and Ip increased from 0. 937 V and 1. 810 μA (Group Ⅱ ) to 1. 701 V and 2. 252 μA (Group Ⅳ )respectively,there was even no passivation in Group Ⅲ (which was the most coarse),so proneness to corrosion enhanced. For specimen with the same surface roughness ,Ep and Ip of Group Ⅳ (1. 701 V and 2. 252 μA respectively),which was placed on polished surface of denture base,was higher than that on tissue surface (Group V , 1. 304 V, 1. 946 μA). Conclusion:From the perspective of corrosion behavior,wrinkly surface should not be adopted when pure Ti prosthesis is used ,and surface roughness on the polishing surface of pure Ti prosthesis should be paid more attention,especially on clasps and connectors,where there is often more force to be exerted.