A random access preamble sending method includes sending, by a terminal device, a first random access preamble to a network device, and sending, by the terminal device during a first time period, a second random access preamble to the network device when the terminal device does not receive a random access response and when a first sending moment arrives, where the first time period is a time window to receive the random access response from the network device, and wherein the first time period comprises the first sending moment.