A method, an apparatus and a system can be used for improving data transmission performance. Specific steps may include determining whether a transmission rate for transmitting data is lower than a reference transmission rate that the data is actually required. If it is lower than the reference transmission rate, a reference working frequency is obtained by querying part of or an entire working frequency band. The reference working frequency corresponds to a transmission rate that is higher than or equal to the reference transmission rate from the working frequency band. Frequency modification indication information is sent to a network access device and a working frequency for communication is modified to the reference working frequency.