The model for characterizing the mode field of polarization-maintaining photonic crystal fiber (PMPCF) is proposed. The on-line mode field testing setup for PM-PCF is established based on the near field spot imaging method and the absolute measurement of mode field parameters is achieved with an infrared camera system. The effect of discharge on the PM- PCF mode field redress is investigated and the evolutions of mode field parameters are also obtained by numerical simulations. The calculation model of the splicing loss between PM- PCF and conventional polarization maintaining fiber is derived, and the low loss splicing condition is also determined and experimentally verified. The result demonstrates that the loss splicing between PM-PCF and conventional polarization maintaining fibers is successfully realized.