An information transmission method, comprising: receiving, by a first communications device, a first signal that is transmitted from a second communications device to the first communication device by using a radio channel, wherein the first signal represents an under an action of the radio channel impacted second signal which was originally sent out by the second device, and wherein information carried by the second signal represents one of M state values, and a specific frequency resource assigned to the second signal and a first sequence corresponding to subcarriers of the specific frequency resource occupied by the second signal meets: the first sequence is directly proportional to a product of a preset second sequence, wherein the second sequence is known by both the first communications device and the second communications device, and a third sequence in a state sequence set, wherein the state sequence set comprises at least M third sequences corresponding to the M state values, any third sequence in the M third sequences is a complex exponential sequence with a linear phase, and elements with an interval of K-1 elements in any third sequence are equal, wherein K and M meet K≥M, M is a positive integer greater than 1, and K is a positive integer less than a length of the third sequence; estimating, by the first communications device, channel information of the radio channel according to the first signal and the second sequence; and determining, by the first communications device according to the channel information of the radio channel and the first signal, the information carried by the second signal. receiving, by a first communications device, a first signal that is transmitted from a second communications device to the first communication device by using a radio channel, wherein the first signal represents an under an action of the radio channel impacted second signal which was originally sent out by the second device, and wherein information carried by the second signal represents one of M state values, and a specific frequency resource assigned to the second signal and a first sequence corresponding to subcarriers of the specific frequency resource occupied by the second signal meets: the first sequence is directly proportional to a product of a preset second sequence, wherein the second sequence is known by both the first communications device and the second communications device, and a third sequence in a state sequence set, wherein the state sequence set comprises at least M third sequences corresponding to the M state values, any third sequence in the M third sequences is a complex exponential sequence with a linear phase, and elements with an interval of K-1 elements in any third sequence are equal, wherein K and M meet K≥M, M is a positive integer greater than 1, and K is a positive integer less than a length of the third sequence; estimating, by the first communications device, channel information of the radio channel according to the first signal and the second sequence; and determining, by the first communications device according to the channel information of the radio channel and the first signal, the information carried by the second signal.