The present disclosure describes a sidelink communication method and a terminal device. The method includes transmitting, by a second terminal device, sidelink control information (SCI) to a first terminal device. The SCI is used by the first terminal device to obtain information of a sidelink reference signal, and includes a first indication field used for indicating the first terminal device to determine resource indication information of the sidelink reference signal. In response to the resource indication information of the sidelink reference signal including frequency domain start position indication information of the sidelink reference signal but not frequency domain length information of the sidelink reference signal, the frequency domain length information of the sidelink reference signal is determined based on pre-configured information or information configured by a network device.