An approach to the analytical dynamic model for spherical parallel mechanisms by means of screw theory was presented. Using screw theory, one and two order effect coefficient matrixes for 2-DOF spherical parallel mechanisms were derived. Analytical dynamic model for spherical parallel mechanisms was established based on numeric-symbolic approach and Kane dynamic equation, in which inertia parameters and geometric parameter as well as generalized coordinates were expressed as symbols. Problem of deriving model matrix elements has been transformed into the problem of solving for driving force under specified conditions by kinematic and dynamic formulae. The numerical examples of analytical code generation for dynamic model matrix elements and simulation calculation were given for illustration. The influence of adjustable parameters on dynamic of 2-DOF spherical parallel mechanisms was studied.