Based on the nonlinear propagation model of ultrafast laser pulses, the polarization dynamics of femtosecond laser pulse in silica is numerically simulated. The degree of polarization and the numerical aperture have effect on the ultrashort laser transmission and the pulse compression. Both the critical degree of the laser polarization and the critical numerical aperture are obtained when the refocusing of laser beams occurs. The results show that by the loose focusing, ultrafast pulses with the linear, elliptic and circular polarizations demonstrate various intensity distribution and plasma filaments structure due to the selffocusing effect. In the temporal domain, the circularly polarized laser, compared with the linearly polarized laser, only shows the selfcompression without the pulse splitting. However, by the tight focusing, three polarized lasers tend to the similar propagation property without the obvious pulse compression.