Abstract: A novel single layer microstrip reflectarray element with multi-resonance structure is proposed in this paper. HFSS soft ware is used to analyze the reflect phase for the designed element. About 430°reflect phase range is obtained with the reflect phase curve nearly linear. A microstrip reflectarray composed of the proposed element is designed for Ku band and a Vivaldi antenna is used as the feed. The results indicate that the gain reaches 27.1 dB at the center frequency, and the half power beamwidth is 4.96°. The gain changes less than 2 dB in the range of 12~15.5 GHz, which shows that the reflectarray has wide band. The Vivaldi antenna and the reflectarray is manufactured and tested, and a well coincide is obtained between the simulation results and the test results.