Abstract: For the two commonly used orho-rectification models in spaceborne SAR, which are collinearity model and range-Doppler (R-D) model, we proposed an analysis for the common and opposite characteristics existing in their principle and solving steps in sequence. Moreover, we made a comparison for the computation result based on the on-site experiment data obtained by corner reflectors as well. Experimental results illustrate that although the two models should not only be based on entirely different principles of hypothesis, but also own different computation results with the same internal physical parameters, the output accuracy of the two models are basically the same.