Based on the double plane representation of the light field, aimed at the effect of light on the way of description influenced by coaxial translation, off-axis translation, coplanar rotation and off-planar rotation, and lens transformation between two reference plane of light field camera, this paper provided the corresponding matrix transformation equations. And using the transformation equations, the imaging model, sampling model, and radiation model of light field camera are established. Besides, on the view of light field coaxial space distance transformation, the digital refocusing process is deduced which can receive clearly imaging in any target scene point after got the imaging by focusing at a point. And moreover, by using the established model, the object is generated by computer simulation, and the model is used for digital refocusing on generation of features, the consistency of digital refocusing image and the directly focused images are verified.