A synchronization information sending method, comprising: obtaining, by a communications node, a pulse per second, PPS, signal, wherein the obtaining a PPS signal includes generating of the PPS signal by a crystal oscillator of the communications node having a global positioning capability; obtaining, by the communications node, a first time instant T1 based on the PPS signal, wherein the obtaining a first time instant T1 based on the PPS signal contains determining, by the communication node, a coordinated universal time, UTC, as the first time instant T1 based on a peak of the PPS signal; receiving, by the communications node, a subframe and an identifier of the subframe that are sent by a base station; obtaining, by the communications node, a second time instant T2 based on the subframe, wherein the second time instant T2 is a time instant at which the subframe arrives at the communications node, wherein the subframe used to obtain the second time instant T2 is a last subframe that is received by the communications node before the first time instant T1, or the subframe used to obtain the second time instant T2 is a first subframe that is received by the communications node after the first time instant T1;determining, by the communications node, a first time difference, TD 1, based on a difference between the first time instant T1 and the second time instant T2; obtaining, by the communications node, a timing advance, TA, corresponding to the base station, wherein the TA has a value equal to a round-trip delay between the communications node and the base station; obtaining, by the communications node, a second time difference, TD 2, based on the first time difference, TD 1, and the TA, wherein the second time difference, TD 2, is a difference between a time instant at which the base station sends the subframe and the first time instant T1; and sending, by the communications node, the second time difference, TD 2, the first time instant T1, and the identifier of the subframe to the base station. obtaining, by a communications node, a pulse per second, PPS, signal, wherein the obtaining a PPS signal includes generating of the PPS signal by a crystal oscillator of the communications node having a global positioning capability; obtaining, by the communications node, a first time instant T1 based on the PPS signal, wherein the obtaining a first time instant T1 based on the PPS signal contains determining, by the communication node, a coordinated universal time, UTC, as the first time instant T1 based on a peak of the PPS signal; receiving, by the communications node, a subframe and an identifier of the subframe that are sent by a base station; obtaining, by the communications node, a second time instant T2 based on the subframe, wherein the second time instant T2 is a time instant at which the subframe arrives at the communications node, wherein the subframe used to obtain the second time instant T2 is a last subframe that is received by the communications node before the first time instant T1, or the subframe used to obtain the second time instant T2 is a first subframe that is received by the communications node after the first time instant T1;determining, by the communications node, a first time difference, TD 1, based on a difference between the first time instant T1 and the second time instant T2; obtaining, by the communications node, a timing advance, TA, corresponding to the base station, wherein the TA has a value equal to a round-trip delay between the communications node and the base station; obtaining, by the communications node, a second time difference, TD 2, based on the first time difference, TD 1, and the TA, wherein the second time difference, TD 2, is a difference between a time instant at which the base station sends the subframe and the first time instant T1; and sending, by the communications node, the second time difference, TD 2, the first time instant T1, and the identifier of the subframe to the base station.