Abstract: In this paper, the theoretical analysis was presented on the major source of the noise in the γ-ray camera. Based on the analysis, the noise power spectrum of the γ-ray camera was calibrated under γ-ray radiation sources (0.2 MeV and 1.25 MeV energy, respectively) of various irradiation dosages. The results show that the noise is mainly induced by the fluctuation of the gain of the MCP image intensifier. The remarkable noise peak occurs nearby the spatial frequency of 0.633 1 mm^-1. And almost the same phenomena are found with both 0.2 MeV and 1.25 MeV radiation energy. Besides, the noise power spectrum is in circular symmetrical distribution, whose intensity rapidly decreases with the increase of the spatial frequency.