To satisfactorily detect the defects and topography of the inner wall of a cylindrical workpiece, this paper proposes a panoramic imaging method based on depth learning and machine vision. Through zoom imaging, this method obtains a multi-focus image sequence of the inner wall of a cylindrical workpiece, and uses a multi-focus image fusion algorithm based on convolution neural network to fuse the inner wall image sequences collected at different depths of field to get a fully focused panoramic view of inner wall. Based on perspective transformation principle of visual imaging, the inverse mapping panoramic mapping is used to improve the inner wall topography reconstruction method and obtain the inner wall topography image of the cylindrical workpiece under a cylindrical coordinate system. Experimental results show that the proposed topography reconstruction method can effectively detect the state of the inner wall, and the imaging quality is optimal.