In order to get photon counting fusion images with better effect, this paper proposes a fusion algorithm based on improved regional energy fusion rules. The photon counting images are obtained by the multi-pixel photon counter (MPPC) single detector in different illumination conditions, and the high-frequency and the low-frequency parts are obtained after wavelet transform of photon counting image. In the high-frequency part of the two source images, the energy of the corresponding region, neighborhood mean square, matching degree and threshold deviation are calculated. And the threshold is determined by pixel values and mean values of regional image. If the matching degree is greater than or equal to the threshold value, the weighted regional energy fusion method is used to solve it. Otherwise, the enhanced pixel value of source image with larger energy in local region is selected as pixel value in the corresponding fusion image. Using improved regional energy fusion rules for image fusion, it is proved that details of photon counting fusion image are clearer and target is easier to recognize，and the values of information entropy, average gradient and spatial frequency are about 20%, 25%, and 30% higher than those of regional energy fusion rules.