Aiming at the analysis of the position and orientation error on the new 3- PRS parallel mechanism with three adjustable pedestals and variable working space,a geometric analytic method for the forward kinematics analysis of the 3- PRS parallel mechanism is proposed,then the analysis of the working platform end- effector error is derived,and what’s more,the position and orientation of the working platform end- effector is obtained by using software emulation when the three pedestals at different positions. The results show that the end- effector error has obvious changes with the different positions of the three pedestals. This study provides a useful guidance for the error compensation of the new 3- PRS parallel mechanism.