MOSFET is an electronic devices with good switching characteristics. It is widely used in circuits, such as power supplies switching , motor drives, lighting dimmer and so on. Relay is another kind of module with switching characteristics. We designed a 4-channel MOSFET switch. It can supply up to four groups of electronic switches to control different circuit blocks respectively. Limited by the working priciples, MOSFET can only be used to control the DC circuit, such as DC-LED screen and so on, but not suitable for AC circuit control. In some extreme cases, it can be used to control 100V/33A DC circuit. However, it is suggested that the controlled DC voltage is more than 9V.