A data transmission method, comprising: sending, by a user equipment, UE, capability information of the UE to an access node of a cellular access network, wherein the capability information of the UE indicates whether the UE supports data transmission both on the cellular access network and on the WLAN; receiving, by the UE, indication information sent by the access node, wherein the indication information comprises a filtering condition, and the indication information is used to instruct the UE to transmit, by using a wireless local area network, WLAN, a traffic flow that meets the filtering condition; determining, by the UE according to the indication information, that a first traffic flow meets the filtering condition; and transmitting, by the UE, the first traffic flow by using the WLAN; wherein the filtering condition comprises a transmission characteristic identifier; the determining, by the UE according to the indication information, that a first traffic flow meets the filtering condition comprises: determining, by the UE, if the first traffic flow matches a first filter and filter information of the first filter comprises the transmission characteristic identifier, that the first traffic flow meets the filtering condition; or, determining, by the UE, if a transmission characteristic identifier of an application program corresponding to the first traffic flow is the transmission characteristic identifier, that the first traffic flow meets the filtering condition. sending, by a user equipment, UE, capability information of the UE to an access node of a cellular access network, wherein the capability information of the UE indicates whether the UE supports data transmission both on the cellular access network and on the WLAN; receiving, by the UE, indication information sent by the access node, wherein the indication information comprises a filtering condition, and the indication information is used to instruct the UE to transmit, by using a wireless local area network, WLAN, a traffic flow that meets the filtering condition; determining, by the UE according to the indication information, that a first traffic flow meets the filtering condition; and transmitting, by the UE, the first traffic flow by using the WLAN; wherein the filtering condition comprises a transmission characteristic identifier; the determining, by the UE according to the indication information, that a first traffic flow meets the filtering condition comprises: determining, by the UE, if the first traffic flow matches a first filter and filter information of the first filter comprises the transmission characteristic identifier, that the first traffic flow meets the filtering condition; or, determining, by the UE, if a transmission characteristic identifier of an application program corresponding to the first traffic flow is the transmission characteristic identifier, that the first traffic flow meets the filtering condition. determining, by the UE, if the first traffic flow matches a first filter and filter information of the first filter comprises the transmission characteristic identifier, that the first traffic flow meets the filtering condition; or, determining, by the UE, if a transmission characteristic identifier of an application program corresponding to the first traffic flow is the transmission characteristic identifier, that the first traffic flow meets the filtering condition.