A auging head of atomic force microscopy (AFM) based on interference of polarized light is designed for high resolution and capacity of resisting disturbance. This AFM head detects the tip displacement based on interference, in order to increase the sensitivity. In the process of design, the feasibility of focal spot on the cantilever is analyzed, and verified with experiment. The experimental result shows that two Wollastton prisms can effectively change the optical-path difference between reference beam and measurement beam, and reduce the size of AFM head. The design of common-path Nomarski interferometer can reduce noise, keep the structure of head compact and make this system useful. The axial resolution of the system can reach up to 1 nm. It can support the research of AFM technology.