Synthetic aperture radar with squint angle has a very wide application prospect. An improved squint imaging algorithm based SPECAN for missile-borne is proposed, which is characterized by its small amount of computation and convenient operation. According to the SAR echo model, traditional SPECAN algorithm has been improved. This algorithm firstly processed echo signals with range walk removal; and then it performed range FFT process, distance migration removal and range compression; at last after azimuthal IFFT process, good SAR imaging results are acquired. Simulation results corroborate the validity of the algorithm.