Near range microwave imaging techniques have broad application prospects in the field of concealed weapon detection, biomedical imaging, non-destructive testing, etc. In this paper, the 3D bistatic imaging geometry based on planar scanning aperture are proposed to be applied to near range microwave imaging, which can obtain the bistatic reflectivity of targets and consequently conduce to classify and identify different targets; Then, this paper establishes the echo model in this imaging geometry, and deduces the 3D bistatic Omega-K imaging algorithm based on the Loffeld's bistatic formula (LBF) method; Finally, through numerical simulation, verifies the imaging geometry and imaging algorithm proposed in this paper.