Combined with short wavelength of the w-band and small volume and low cost advantage of the FMCW SAR, much attention has been paid to the application of W band FMCW SAR with high resolution imaging to close small target imaging. This paper introduces a W-band Rail FMCW SAR used to small target imaging in near-distance. Based on the system parameters simulation and design, the design of the system scheme is also given. In addition, using the modified RD imaging algorithm to get the point target simulation result. The result proves the feasibility and reliability of the system.