To provide the basis for the methods of vegetation height inversion by using single-baseline PolInSAR SAR data and explore a more effective inversion method, the European Space Agency (ESA) Toolbox PolSARPro was used to simulate L-band (L=23cm) PolInSAR SAR data with an average vegetation height of 18m. The DEM difference, RVoG, SINC, Hybrid, and Hybrid method were studied based on coherent optimization. The vegetation height ranged from 3m to 30m was analyzed with 1104 sample points in the middle region of the image. Giving a 3D image, range profile image with azimuth of 48 and statistical image of vegetation height and topographic phase were used to compare the performance of five methods. Compared with the real value of 18m, the descending order of vegetation height means was SINC, Hybrid, improved Hybrid, RVoG and DEM difference method. The difference between the improved Hybrid inversion method and the real value was the smallest as 0.12m, smaller than Hybrid of 0.31m. RMSE of the improved Hybrid, Hybrid, SINC, RVoG and DEM difference was 1.06m, 1.48m,3.49m, 7.51m and 8.04m, respectively. The vegetation height of the improved Hybrid method had the smallest difference and RMSE. The estimated topographic phase average value of the improved Hybrid, RVoG/Hybrid and DEM difference method was -0.018rad, 0.011rad and 0.1rad;RMSE was 0.045rad, 0.054rad and 0.15rad;and mean value of absolute value was 0.03rad, 0.04rad, and 0.1rad, respectively. The topographic phase of the improved Hybrid method was approximately the closest to the simulated and had the smallest RMSE and the mean of absolute value. Improved Hybrid inversion method produced the best result among the five methods, combining the merits of Hybrid with the coherent optimization, with the smallest difference between real value and RMSE of vegetation height and topographic phase. The Hybrid method was improved based on the coherent optimization and the accuracy of vegetation height was analyzed with the ground phase estimation results to compare the five methods.