The autoalignment technique is studied for the PM fiber (PMF) of matching refractiveindex(MRI). The polarization observation by lenseffecttracing technique(POL) is introduced. Based on the POL,an autoalignment system is designed and its performance is then tested. Different lightintensity distribution characteristic is found on the different observation surfaces in a series of experients. The widest range of adjustment is achieved when the observation surface corresponds to a lightintensity distribution with five characteristic points. This means it is easier to focus.The fivepoint method is presented after analysis of the curves of the five characteristic points with respect to the azimuth angle of the optical fiber.By comparison with the POL,this method is easier to be realized and has higher measurement accuracy,so it is suitable for autoalignment system.