To improve the azimuth resolution performance which depends on the reconstruction angle in rotating synthetic aperture radar (ROSAR) system, a novel curved orbit approximation method based on the resampling and rotation of the transmitted and received pulse position is proposed. The approximation errors are calculated via an extended Taylor expansion and are compensated in the raw data domain. Precise two-dimensional (2-D) spectrum is derived and high resolution image is formed using extended omega-K algorithm for large scene. Feasibility and resolution performance of the proposed method are validated through simulation results.