A method, a user equipment, and a network side device for monitoring a physical downlink control channel are provided. The method includes: receiving a physical layer signaling or an MAC layer signaling from a network side, wherein the physical layer signaling or the MAC layer signaling indicates a monitoring behavior of the UE or a plurality of UEs including the UE with respect to a PDCCH; determining the monitoring behavior of the UE with respect to the PDCCH according to the physical layer signaling or the MAC layer signaling.