To solve the problem of missing digital fringe information when the binocular digital grating projection method is used to measure the objects with low surface reflectance such as coal, an adaptive multi-exposure image fusion binocular digital grating projection method is proposed in this paper. First, the initial images collected under initial exposure are segmented using the K-means clustering analysis method, and then the optimal exposure time for each pixel cluster is calculated. Second, images of projection white light and fringes are acquired based on the calculated optimal exposure time. Then, a method of multi-exposure image fusion is employed to synthesize new fringe images. Finally, coal block three-dimensional morphology reconstruction is performed using multi-frequency heterodyne method and phase matching. Experimental results show that the proposed method achieves a point cloud reconstruction rate of over 99% when photographing coal blocks, effectively overcoming the measurement difficulties caused by low reflectivity of the object being measured, reconstructing the surface morphology of coal blocks well.