Locking the output frequency of the laser to a suitable reference frequency can effectively improve the frequency stability of the laser, suppress the frequency fluctuation of the laser, and achieve laser frequency stabilization. In this paper, we study the two-color polarization spectroscopy (TCPS) based on the 6S1/2-6P3/2-70S1/2 ladder-type three-level system in a cesium atomic vapor cell at room temperature, and use this TCPS to achieve modulation-free laser frequency stabilization. In the experiment, a linearly polarized 852 nm laser as probe light, resonant at 6S1/2(F=4)→6P3/2(F'=5) transition, a circularly polarized 509 nm laser as coupling light, and laser frequency was scanned near 6P3/2(F'=5)→70S1/2 transition. The circularly polarized coupling light pump atoms live in different Zeeman states to achieve anisotropy in the medium. We obtained the TCPS of the Rydberg state by detecting the anisotropy of the atomic medium by polarized light field, and analyzed it theoretically. And we experimentally measured the dependence of TCPS on the laser power of 852 nm linear polarization probe light and 509 nm circularly polarized coupling light, and the results showed that due to the influence of atomic coherence effect, the linewidth of TCPS was significantly suppressed with the change of coupling power, and due to the influence of optical pumping and power broadening, the coherent effect of the atomic system would be destroyed, and the TCPS linewidth would increase significantly with the increase of probe power. Using this Rydberg state TCPS, we lock the frequency of the 509 nm laser corresponding to the Cesium 6P3/2 (F'=5)→70S1/2 transition, and the frequency fluctuation of the 509 nm laser is significantly improved compared with the frequency fluctuation during free running at the same time. This TCPS provides a modulation-free technique that can be used for frequency locking of laser systems matched to multiple Rydberg states, which is important for precision measurements based on the Rydberg state.