Abstract: Because of the complex of the integral function and the observation equation, it is very difficult to estimate the trajectory parameters according to the Bayes method. The Kalman Filter is often divergence. For rebuild of the trajectory, a approximate filter of condition rules with recursive formula which based on the Bayes method is put forward in the paper. It can estimate the state parameters of the system exactly. The simulation demonstrates the divergence of estimation and accuracy problems for project can be solved by this approach.