Fundus examination plays an important part in a medical setting. The fundus camera is one of the detection instruments used in obtaining fundus images, which can reflect information about disease and other conditions. However, traditional fundus cameras have many disadvantages in regard to data sharing, image recognition, and processing, as well as doctor-patient communication. In recent years, mobile medical systems have gradually become more prevalent in medical and health system environments. In this paper, we propose a design method for a smartphone fundus camera consisting of an illumination system and an imaging system. The end of the system can be combined with a smartphone to take the fundus images directly. We manufactured a prototype, designed an artificial eye model, and carried out a series of experiments. The results show that we can get fundus images clearly, and the imaging system will be able to correct refractive errors ranging from -8D∼+8D. The spatial resolution of the system is up to 15 µm. This is a portable device with an overall size of 160mm×160mm×80mm and a weight of 540 g. It has the advantages of lower price, simple operation, high resolution, and compact size, making it suitable as a portable ocular monitoring device.