A wireless communication method and a terminal device are provided. The terminal device can flexibly start a hybrid automatic repeat request (HARQ) round trip time (RTT) timer, thereby saving power. The method includes monitoring, by a terminal device, a physical downlink control channel (PDCCH) in a discontinuous reception (DRX) period, where the uplink grant indicates an asynchronous HARQ process used for transmitting a physical uplink shared channel (PUSCH). The method further includes starting, by the terminal device, an uplink HARQ RTT timer for the asynchronous HARQ process at a first moment after detecting the PDCCH.