A method for transmitting a signal between user equipments, comprising: inserting, by the first user equipment, a reference signal into a first subframe according to a reference signal insert mode corresponding to the first subframe; sending, by a first user equipment, the first subframe into which the reference signal is inserted to a second user equipment, so that the second user equipment parses the first subframe according to the reference signal inserted into the first subframe; performing, by the second user equipment, channel estimation by using the reference signal inserted into the first subframe when receiving the first subframe; demodulating and decoding, by the second user equipment, the first subframe to restore an original D2D signal after a channel is estimated, wherein a quantity of orthogonal frequency division multiplexing, OFDM, symbols comprised in the first subframe is less than a quantity of OFDM symbols comprised in a second subframe, and the second subframe is a subframe received by a network device; and the second subframe comprises 14 OFDM symbols, the first subframe comprises 13, 12, or 7 OFDM symbols, and the OFDM symbol comprises valid data and a cyclic prefix, such that a time length of a cyclic prefix of each OFDM symbol in the first subframe is increased in respect of the second subframe, and therefore, a time difference between a time at which the first subframe sent by the first user equipment reaches the second user equipment and uplink timing of the second user equipment is less than the time length of the cyclic prefix of each OFDM symbol in the first subframe, thereby avoiding interference between symbols and improving performance of a D2D ProSe. inserting, by the first user equipment, a reference signal into a first subframe according to a reference signal insert mode corresponding to the first subframe; sending, by a first user equipment, the first subframe into which the reference signal is inserted to a second user equipment, so that the second user equipment parses the first subframe according to the reference signal inserted into the first subframe; performing, by the second user equipment, channel estimation by using the reference signal inserted into the first subframe when receiving the first subframe; demodulating and decoding, by the second user equipment, the first subframe to restore an original D2D signal after a channel is estimated, wherein a quantity of orthogonal frequency division multiplexing, OFDM, symbols comprised in the first subframe is less than a quantity of OFDM symbols comprised in a second subframe, and the second subframe is a subframe received by a network device; and the second subframe comprises 14 OFDM symbols, the first subframe comprises 13, 12, or 7 OFDM symbols, and the OFDM symbol comprises valid data and a cyclic prefix, such that a time length of a cyclic prefix of each OFDM symbol in the first subframe is increased in respect of the second subframe, and therefore, a time difference between a time at which the first subframe sent by the first user equipment reaches the second user equipment and uplink timing of the second user equipment is less than the time length of the cyclic prefix of each OFDM symbol in the first subframe, thereby avoiding interference between symbols and improving performance of a D2D ProSe.