A new two frequency laser alignment system is developed which consists of two Wollaston prisms with the same structure. One is for measurement; another for compensation. Using phasemeter, the two prisms can be moved out off the beam, so the system can be used to measure coaxality. The displacement drift and angle drift of laser beam are compensated by the optical system automatically. The paper analyzes those adaptive characteristic in theory. Experimental result is in concordance with theoretical analysis.