Forward kinematics analysis of a novel 5-DOF parallel mechanism using tetrahedron configurations is presented.Such mechanism is suitable to many tasks requiring less than 6 DOFs.It consists of a movable platform connected to the base by five identical 6-DOF active limbs plus one active limb with its DOF being exactly the same as the specified DOF of the movable platform,which leads to its legs’ topology 4-UPS/UPU.Based on the tetrahedron geometry,both closed-form solution with an extra sensor and numerical method using iterative algorithm are employed to obtain the forward kinematics solutions of the mechanism.Compared with the conventional methods,the proposed closed-form solution has the advantages in automatically avoiding unnecessary complex roots and getting a unique solution for the forward kinematics.Finally,an example shows that the proposed numerical algorithm is so effective that it enables a real-time forward kinematics solution to be achieved and the initial value can be chosen easily. Forward kinematics analysis of a novel 5-DOF parallel mechanism using tetrahedron configurations is presented. Such mechanism is suitable to many tasks requiring less than 6 DOFs.It consists of a movable platform connected to the base by five identical 6-DOF active limbs plus one active limb with its DOF ​​being exactly the same as the specified DOF of the movable platform, which leads to its legs’ topology 4-UPS / UPU.Based on the tetrahedron geometry, both closed-form solution with an extra sensor and numerical method using iterative algorithm are employed to obtain the forward kinematics solutions of the mechanism. Compared with the conventional methods, the proposed closed-form solution has the advantages of automatically avoiding unnecessary complex roots and getting a unique solution for the forward kinematics. that the proposed numerical algorithm is so effective that it enables a real-time forward kinematics solution to be achieved and the initial value can be ch osen easily.