A common-path radial shearing phase-shifting interferometer with adjustable fringe contrast is proposed against some disadvantages of conventional one, such as non-adjustable fringe contrast, low measurement accuracy of shearing phase difference recovery or complicated phase-shifting method, and difficulty of optical system adjustment. The contrast adjusted continuously is achieved using polarization beam splitters in this system, and the four-stepping phase-shifting interference is also carried out by the polarization phase-shifting technology. The fringe contrast which is one of the main influence factors about wavefront reconstruction accuracy is analyzed theoretically and verified experimentally. The actual aberration generated by liquid crystal spatial light modulator (LC-SLM) is measured experimentally. The results indicate that the common-path radial shearing phase-shifting interferometer can gain the highest fringe contrast. The research results of the relationship between the polarizing angle and fringe contrast can provide an important theoretical basis for the design and establishment of related optical systems.