A method of DRX operation enhancement in adaptive TDD systems is proposed. A UE configures and enters DRX operation in an LTE/LTE-A mobile communication network. The UE obtains adaptive TDD configuration information from a base station. The adaptive TDD configuration information comprises an actual TDD configuration and a reference TDD configuration. The UE performs DRX timer counting and HARQ timer counting based on the reference TDD configuration. The UE also synchronizes DRX status with the base station. With the reference TDD configuration, it can avoid the potential misunderstanding between eNB and UE regarding DRX and HARQ RTT timing when TDD configuration changes.