The primary goal of this paper is to analyze the kinematic and dynamics of a 3PUS-S(P) parallel spherical metamorphic mechanism. It consists of a moving platform, base platform, three PUS legs and one middle S(P) metamorphic leg. A complete description of the position and orientation of the moving platform requires six variables. Since the parallel metamorphic mechanism has three degrees of orientation freedom in 1st configuration and extra one degree of translational freedom in 2nd configuration, which implies that only three variables are independent in 1st configuration and four variables in 2nd configuration. Firstly, the constraint equations describing the six motion coordinates of moving platform are derived and kinematic equations are established based on vector algebra method. Secondly, inverse dynamics equations of this metamorphic mechanism are established based on the Newton-Euler formulation. According to geometric and physical parameters of real mechanism, required driving and constraint forces can be obtained when the motion of moving platform and working load are given by solving the inverse dynamics equations. Furthermore the simulation result illustrates that 3PUS-S(P) parallel metamorphic mechanism can avoid impact damage by activating the constrained prismatic pair in middle leg.