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Indoor synthetic aperture radar (SAR) obtains the image of a room with a track at one end of the room. Imaging algorithms used in this geometry should preserve the precise hyperbolic range history. Back-Projection algorithm (BPA) and Range-Migration algorithm (RMA) are two typical algorithms that could be used in indoor SAR imaging applications. The performance of the two algorithms is compared using the data collected by a 77 GHz radar, and the specific characteristics of indoor SAR images are analyzed. The enclosed environment causes strong multiple reflections and produces mirror images beyond the physical size of the room. When implementing RMA, the aperture data should be severely zero-padded or a window in range-azimuth-frequency domain should be used to avoid the aliasing in the image. The imaging geometry varies at different locations in the room, and the targets with smaller spectrum support will be attenuated by the wavenumber domain interpolation in RMA. These results are helpful in indoor SAR image comprehension and object identification.