Abstract: The paper introduced principle of HARQ technology of LTE system, established simulation platform of LTE system downlink based on type III HARQ, and simulated and compared BLER of LTE system with and without HARQ technology. The simulation result showed that HARQ technology not only reduces BLER of LTE system effectively, but also makes LTE system to get the same as or better communication quality under the condition of low signal-to-noise ratio, namely HARQ technology can improve communication quality of users who are in cell coverage edges and poor radio channels.