Singularity is an inherent nature of mechanism, which make a significant impact on mechanism’s work performance. The singularity loci of a spatial rotation 3-SPS-1-S parallel mechanism was studied. The parallel robot kinematics model was constructed. The equations for inverse displacement and velocity kinematics were derived, and the Jacobian matrix of this mechanism was analyzed. The singularity criterion was proposed，and two types of singularity were determined to be singular configuration. Manipulability degree was introduced to evaluate kinematical performance of the parallel manipulator for the singularity loci analysis. The results showed that the parallel mechanism has a good manageability and kinematics performance in the specified task space, but the special motion position should be turned away to avoid the occurrence of singularity.