The ray solutions of paraxial equation for imaging electron optics have been explored by an ideal model of combined electromagnetic concentric spherical system in the present paper. The exact analytical expressions of rotational angle as well as two special solutions of paraxial equation in this system have been firstly derived, and the paraxial imaging properties have also been investigated. The results have been generalized to the bi-electrode electrostatic concentric spherical system, the homogeneous and parallel combined electromagnetic system, and the electrostatic proximity system.