A method for Downlink Control Information (DCI)-based Physical Downlink Control Channel (PDCCH) monitoring adaptation is proposed. A User Equipment (UE) performs a Discontinuous Reception (DRX) operation. The UE detects a UE-specific DCI format during the DRX operation, wherein the UE-specific DCI format includes a bit field that indicates an adaptation on PDCCH monitoring. The UE adjusts a PDCCH monitoring periodicity in a DRX active time of the DRX operation according to the bit field.