Abstract: An optimal synthesis method of planar linkage mechanism for continuous path generation was put forward, which would find the interpolation nodes of planar linkage mechanism-s trajectory generation mechanism, for bi-objective of trajectory and velocity. The interpolation nodes were entrusted with the physical meaning of the velocity by this method. The optimal synthesis model was set up based on the minimization of the error between the path-generating point in the coupler curve and the prescribed position, while the nonlinear optimization algorithm of BFGS(Broyden-Fletcher-Gddfarb-Shanno) quasi-Newton was adopted to find the global optimum solution to approximate kinematic synthesis of planar linkage. With the uniform rotation of the crank, the optimization algorithm calculated the planar linkage mechanism, satisfied the requirements of our bi-objective, and actualized the expectant target. The validity and effectiveness of the proposed method were illustrated by comparing the optimization results of four-bar mechanism and five-bar mechanism.