UART (Universal Asynchronous Receiver Transmitter) is widely used in spaceborne instruments internal communication. Aiming at the complex electromagnetic environment in space, the circuit is sufferring from cosmic rays and Single-Event Upset, this paper studies the UART circuit design method for space environment applications. The hardware method useanti radiation anti fuse FPGA and military grade communication interface chip to realize the bus topology UART communication connection structure. The software method use hardware description language to complete the serial communication protocol, combined with the Triple Modular Redundancy serial TMR, parallel TMR technology, digital filtering technology, enhance the fault-tolerant ability of the system, improve the reliability of the system. This paper gives operational principle and implementation block diagram of UART transmitting and receiving circuit. The experimental results show the effectiveness of the method.