3-RPS/(H) Metamorphic parallel mechanism based on conventional mechanisms is proposed in this study. In contrast to the 3-RPS mechanism, the 3-RPS/(H) mechanism comprises a novel intermediate metamorphic limb. The different constraints provided by the intermediate metamorphic limb and locking device enhance the dexterity of the metamorphic parallel mechanism. The configurations of the 3-RPS/(H) metamorphic parallel mechanism are analyzed and their degrees-of-freedom are obtained. Additionally, an inverse kinematic analysis of the mechanism is performed, and its workspace is compared with that of a conventional 3-RPS parallel mechanism with similar parameters. The results demonstrate that the 3-RPS/(H) metamorphic parallel mechanism exhibits better dexterity than that of the 3-RPS mechanism. Moreover, the effects of different structural parameters of the metamorphic parallel mechanism on the workspace are analyzed. Finally, the singularity analysis of the mechanism is performed. The results provide a theoretical basis for the design and optimization of mechanical legs.