This paper presented a fast forward algorithm for 3—RPS (revolute-prismatic-spherical) parallel mechanism. Based on the structure feature of 3—RPS parallel mechanism, firstly, a group of position and orientation coordinates were calculated as the initial value, then the coordinates of each hinge fulcrum on the platform by means of reverse algorithm were obtained and adjusted. No derivative operation or Jacobi matrix inverse operation was needed in proposed algorithm. It effectively reduced the computational load, and the formula was simple. In the same computing environment, the calculation experiment results showed that the amount of programming of the proposed algorithm was only 40% of the existing algorithms, the calculation speed of the proposed algorithm was about 1.5 times of the existing algorithms to achieve the same accuracy. It can be applied to online control. 