The light field camera is used in the wavefront sensing field because of its simple structure, large field of view, high utilization rate of light energy, etc. However, there are some limitations in the traditional light field camera such as low linearity, the obvious step change of the slope response, low reconstruction accuracy and so on. To overcome the above limitations, this paper has effectively improved the traditional light field camera and proposed a new type of defocused light field camera structure to improve the accuracy of wavefront measurement. Simulation studies show that the reconstruction accuracy of the light field camera varies with the distance between the microlens array (MLA) and the focal plane of the main lens. As the distance increases, the re-construction accuracy increases first and then decreases, and there is an optimal defocus amount related to the wavefront distortion, which can help to reach the maximum reconstruction accuracy. This method can improve the accuracy of wavefront measurement and have broad application prospects in the fields of astronomical observation, precision detection, remote sensing imaging and so on.