Based on the problem that side-looking SAR can not image in flight direction with high azimuth resolution, an innovative forward-looking SAR system is studied. The operation mechanism and feasibility of high azimuth resolution are analyzed. According to the spatial geometry and the model of echo signal, chirp scaling algorithm is proposed for forward-looking SAR. The phase compensation factors and realized steps of algorithm are given. Raw data of forward-looking SAR is simulated, and image is achieved by using the chirp scaling algorithm proposed in this paper. The imaging effect is analyzed, and imaging quality is consistent with theory value. Simulation results demonstrate the validity of the algorithm.