Based on the screw theory, the degree of freedom of the 3-PPR parallel mechanism was computed, also the kinetic characteristic was analyzed according to its structural features, and the integrated inverse kinematics was established based on the analytic method. In order to solve the problem of parallel mechanism forward kinematics, this paper proposed a method that translated this problem into objective function optimization, and also built its mathematical model. By improving the basic ant colony algorithm effectively, an ACA was developed for solving the continuous optimization problem. Then this method was used to solve the forward kinematics problem of the 3-PPR parallel mechanism, and it was put into simulation by Matlab. Compared with traditional numerical method, this improved ACA was better at global optimization, and it could avoid the unfavorable effects caused by initial values, so did the local optimal values, also the calculation process will be much simpler without solving the Jacobian matrix and its inverse matrix. Then it is proved that this method is useful for solving the forward kinematics of common parallel mechanisms.