Abstract: It is difficult for conventional parallel mechanisms to improve the terrain adaptability of robotic legs due to its poor motion flexibility. Therefore, a 2-PrRS+PR(P)S metamorphic parallel mechanism is presented for robotic legs based on rotatable-axis revolute pairs. Firstly, the degrees of freedom of three configurations of the mechanism are analyzed. Secondly, the inverse kinematic model of the mechanism is established and the constraint conditions and the ranges of the key parameters are given. Furthermore, the workspace point-cloud of the mechanism is obtained by Monte Carlo method, and the volume of the workspace is calculated using the adaptive mesh method. Compared with the parallel mechanism without metamorphic properties, the shape of the calculated workspace is obviously different under the same parameters, and the workspace volume is 29.36% larger. Finally, the influences of the key structural parameters on the workspace volume are analyzed. It provides the basis for the dimension synthesis of the metamorphic parallel mechanism.