The focusing method can be used to achieve continuous change of the focal length, so that the optical components at different object distances can be detected online. However, the focusing process is complicated and requires high accuracy of the focusing displacement. Defects of optical components within the depth of field cannot be distinguished, making it difficult to achieve real online detection. Therefore, this paper proposes an online detection method for optical component defects based on camera arrays. First, the imaging model of the camera array is established, and the expressions of digital refocusing and the expressions of spatial resolution are given. Then MATLAB is used to simulate the camera array imaging process and digital refocusing process. Finally, experimental verification was conducted. The camera was driven by a two-dimensional stage to image the surface defects of multiple optical elements at different object distances, and an array camera image was obtained. The digital defect refocusing algorithm was used to obtain the surface defect distribution of optical elements at different object distances information. The experimental results show that the online detection technology of optical component defects based on camera array can simultaneously detect the optical components located in the depth of field range. This method has certain application value in the online detection of optical component defects.