As one of the important components of millimeter-wave imaging radar, antennas must have good performance, wide bandwidth, lower sidelobes, high-gain, low profile and easy to be integrated with RF front-end characteristics. This article presents design of CPWG-feed microstrip antenna array with lower sidelobe level at the operating frequency of 77GHz which can be applicated in MIMO imaging radar. According to the measurement results, radiation in sidelobes level of both E-plane and H-plane are below -15dB, the gain of the radiation is larger than 21dBi at the operating frequency 77GHz, the beamwidth of E-plane is 13.4degree, H-plane is 12.5degree. The feeding impedance is 50ohm CPWG transmission line, and frequency band width is larger than 5GHz.