Grinding wheel passivation is an inevitable phenomenon during grinding process. It has important guiding significance for the formulation of grinding technique to unveil the passivation rule and generation mechanism. Taking grinding efficiency as evaluation indicator, the passivation curve of grinding wheel during full passivation period under the constant-force grinding condition is established through experiments in this dissertation, which is divided into three stages according to passivation speeds and passivation patters, i.e. early passivation stage, stable passivation stage and sharp passivation stage. Of which, the passivation speed is the slowest but with the highest grinding efficiency in early passivation stage. The change of passivation curve with the time is a process from concave to convex, which is totally different from the wearing process of grinding wheel in this stage. With combination of experiment conditions and wearing characteristics of grinding wheel, the passivation rule and its generation reasons are discussed deeply. Furthermore the exponential function y = abx is adopted to make fitting for passivation curve based on the scatter plot of stable passivation stage and regression equation is derived through the fitting result of origin thus to testify the correctness of the inference.