CMOS image sensor has been widely used in the field of visible image. It has the characteristics of low cost, low power consumption and high integration. How to transmit the collected image data effectively and improve the transmission distance is one of the main problems in practical application. In addition to the advantages of providing long-distance transmission, Ethernet has the characteristics of high transmission efficiency, simple structure and reliable operation. This paper describes a design scheme of Ether- net transmission system based on CMOS image sensor. Image data is collected by CMOS image sensor, image processing is realized by FPGA, and transmission is carried out through Ethernet interface. The method of displaying image on PC meets the application requirements of the design.