Abstract: Double-plane multi-function nuclear medical imaging system can support both Positron Emission Tomography Imaging(PET) and Single Photon Emission Imaging(Gamma camera). It is a "multi-use" device which can switch operating mode between double plane PET and γ camera using tractable collimators. Considering the requirements of this special operating mode and the accuracy of the mechanical assembly, it is particularly important to process a series of geometric calibration before data acquisition. After that the calibration factors can be used in data correction or image reconstruction. In this paper, we studied the influence of system geometry offset on image quality and established a set of calibration and correction methods based on the parametric representation of these factors. The performance of correction accuracy was evaluated based on the Monte Carlo simulation data. The results showed that the method is effective, feasible and simple.