This article proposed the design of UART based on SmartFusion , expounds the universal asynchronous occurrence device functions and features of UART, using hardware description language Verilog to introduce each module , and the simulation results are given.Put the UART core functionality in FPGA can greatly improve the efficiency of SmartFusion Cortex-M3, the UART interface circuit has the advantages of simple structure, easy upgrade, high stability, can be flexibly applied to various communication systems.