A data transmission method, wherein the method comprises: receiving, by a device in a first basic service set, a data frame sent by a device in a second basic service set, wherein the data frame sent by the device in the second basic service set comprises a preamble sequence and a Medium Access Control frame; transmit power of the preamble sequence is first power; transmit power of the Medium Access Control frame is second power; and the first power is higher than the second power; if the data frame received by the device in the first basic service set comprises the preamble sequence but does not comprise the Medium Access Control frame, setting a network allocation vector value according to a signal field in the preamble sequence; and transmitting data according to the network allocation vector value, characterized that when normal transmit power of an access point in the first basic service set is lower than a threshold, the network allocation vector value comprises a first network allocation vector value and a second network allocation vector value, and the method further comprises: if the data frame received by the device in the first basic service set comprises the preamble sequence and the Medium Access Control frame, setting the first network allocation vector value according to a duration field in a frame header of the Medium Access Control frame; and the setting a network allocation vector value according to a signal field in the preamble sequence comprises: setting the second network allocation vector value according to the signal field in the preamble sequence. receiving, by a device in a first basic service set, a data frame sent by a device in a second basic service set, wherein the data frame sent by the device in the second basic service set comprises a preamble sequence and a Medium Access Control frame; transmit power of the preamble sequence is first power; transmit power of the Medium Access Control frame is second power; and the first power is higher than the second power; if the data frame received by the device in the first basic service set comprises the preamble sequence but does not comprise the Medium Access Control frame, setting a network allocation vector value according to a signal field in the preamble sequence; and transmitting data according to the network allocation vector value, characterized that when normal transmit power of an access point in the first basic service set is lower than a threshold, the network allocation vector value comprises a first network allocation vector value and a second network allocation vector value, and the method further comprises: if the data frame received by the device in the first basic service set comprises the preamble sequence and the Medium Access Control frame, setting the first network allocation vector value according to a duration field in a frame header of the Medium Access Control frame; and the setting a network allocation vector value according to a signal field in the preamble sequence comprises: setting the second network allocation vector value according to the signal field in the preamble sequence. if the data frame received by the device in the first basic service set comprises the preamble sequence and the Medium Access Control frame, setting the first network allocation vector value according to a duration field in a frame header of the Medium Access Control frame; and the setting a network allocation vector value according to a signal field in the preamble sequence comprises: setting the second network allocation vector value according to the signal field in the preamble sequence.