A design of 4-wire touch screen interface based on ADS7846 is proposed, in order to solve the problem that the analog to digital sample of touch screen is easily interfered and reduce the error of measured value. The interface circuit sample the data of touch screen by ADS7846, and the SPI of C8051F320 carried out measure command and measure data transfer to ADS7846. By taking the application of the interface circuit in touch screen an example, analyze the problems of interface circuit then find a solution to those. The actual application shows that the design is reasonable.