Abstract: High Purity Germanium(HPGe) detectors have been widely used in γ spectroscopy. The add-back performance of Clover type HPGe detector is studied based on Monte Carlo simulation. We have simulated the energy spectrum from a single crystal and the Compton scattering probability of γ ray between different crystals. Good agreements have been achieved between the simulated results and experimental data. Afterwards the add-back performance is further studied in terms of γ ray multiplicity and the distance between γ source and the detector. The studies revealed that the higher multiplicity (M = 6 ) affects slightly on the add-back factor at 25 cm distance, mainly in the low energy region. With the distance decreases, the add-back factor changes dramatically. Typically, in the situation of 5 cm distance and M = 6 , the add-back analysis is not recommended.