The current induced magnetic switching (CIMS) effect could occur without the magnetic field in nano-scale pseudo-spin valves that have the potential perspective for application in nonvolatile magnetic random access memory. In this paper, spin transport process in the pseudo-spin valve nanopillars has been investigated with macroscopic double conducting channel diffusion model. Dynamic equation of the magnetization of free layer is established with the consideration of the influence of transverse component of the magnetization vector of free layer. And the boundary conditions of the spin current continuity and chemical-potential-split equality are employed. The critical current in CIMS effect is calculated. The influences of the conductance mismatch of ferromagnetic and nonmagnetic layers and longitudinal applied field on the critical current is interpreted.