The light field camera is a new camera structure that put a microlens array in front of image sensor. It can not only record the intensity and color of light at different positions, but also record the direction information of light in different positions, so that the depth map and high-order phase map of the target scene can be calculated. This technology is limited by the depth of field and resolution, and the resolution is reduced when a large depth of field is achieved. Its structural characteristics were analyzed and the relationship between the depth of field and the resolution was derived, and the change curves were ploted for selected design parameters. Based on this, a design method of a novel light field camera based on a microlens array with four types of focal lengths was proposed, which can obtain large depth of field and control the decline degree of resolution in an acceptable range. The simulation results show that compared with the three types of focal length microlens arrays, the depth of field of the four types of focal length microlens arrays designed can be increased three times, and the resolution can reach 18.9% of the ordinary cameras.