Maritime traffic safety management and emergency rescue have put forward higher requirements for sea surface target detection in recent years. As an active remote sensing method, SAR can provide all-day and all-weather remote sensing detection information, and it is extremely urgent to search and detect sea surface targets in wide-area with high effectiveness. This paper presents the investigation and verification of circular scanning synthetic aperture radar (CSSAR) system for targets imaging and detection in a wide-area of sea surface, parameters affecting the imaging performance of the system are discussed, flight experiment for sea surface target detection is introduced, using airborne CSSAR system. The most fitting distribution based on probability density function (PDF) of sea clutter is obtained by the statistical analysis of sampled sea clutter data, CFAR target detection based on this sea clutter model is realized. The imaging and detection results of ships on the sea surface during the experiment are given, and the resolution performance and location result of angle reflector with fixed position are evaluated. It will be shown that the CSSAR system can achieve wide-area target detection under sea-clutter efficiently.