Abstract: In order to improve the efficiency and universality of the forward kinematics solution of six-degree-of-freedom parallel mechanisms, a forward kinematics solution algorithm of 6-UPS (universal-prismatic-spherical) mechanism is proposed. Firstly, two angle sensors are added to the Hook hinge of any branch of the 6-UPS mechanism, and the rotation angles in the two directions of the Hook hinge are measured. Then 12 equations are constructed based on the rotation matrix, and a simple one-variant quadratic equation system is obtained by reducing the order of equation through algebraic elimination. Finally, the forward kinematics solution of the 6-UPS mechanism is obtained. The proposed method is verified by the numerical examples, and the definite forward kinematics solution is obtained. The method not only reduces the difficulty of data processing, but also solves a unique forward solution, and therefore the problem is avoided that there are multiple forward solutions in parallel mechanism.