Embodiments of this application provide a data transmission method, with step including receiving, by user equipment, a first message, where the first message is used to instruct the user equipment to activate a reflective quality of service RQ mechanism; generating, by the user equipment, an implicit quality of service implicit QoS rule according to the RQ mechanism; receiving, by the user equipment, a second message, where the second message is used to instruct the user equipment to stop using the RQ mechanism; and stopping, by the user equipment, using the RQ mechanism, and deleting the implicit QoS rule. The user equipment receives the second message indicating that using of the RQ mechanism needs to be stopped, and deletes the implicit QoS rule, so as to implement switching between an explicit QoS rule and the implicit QoS rule, and flexibly configure a QoS rule for uplink data according to a policy of an operator.