The algorithm for manipulator trajectory planning based on cubic splines relates to the inversion of the matrix with higher order, and hence, the operation becomes very complex. As a result, the response rate of the manipulator was reduced certainly. In view of this situation, a recursive algorithm to obtain the coefficients of cubic splines was put forward. The recursive algorithm did not require any matrix inversion, and the initial values of recursion came from the boundary conditions expressed by recursive formula. The methods to determine initial values and the recursive formula were presented according to three different boundary conditions. Simulation result showed that the improved algorithm not only can simplify the computes, but also can obtain desired coefficients of cubic splines.