In this paper, near-field microwave imaging system based on side-looking circular scanning is studied. It can solve the problem that the traditional turntable imaging system can not focus the targets with large angular rotation very well. The proposed system introduces not only the sparse sampling technique in frequency domain, but also the fast convolution algorithm in angular domain. The advantage of the proposed method is that it can obtain the high resolution image quickly. The resolution of the proposed method is deduced according to point spreading function. The sampling criterion is then presented in both frequency domain and angular domain. The proposed method is testified by both simulation results and experimental results. The results show that the proposed method can be used to acquire high quality and high resolution image.