A method for processing a CSI processing unit, an apparatus, and a system are disclosed. The method for processing a CSI processing unit comprises: UE receives first signaling from a base station, where the first signaling is used to instruct to deactivate a first cell that provides a service for the UE, or used to instruct the UE to switch from a source BWP to a target BWP; and when target information satisfies a preset condition, the UE processes a first CSI processing unit by using a first processing manner corresponding to the target information, where the target information includes at least the first signaling, the first CSI processing unit is a CSI processing unit for measuring a first downlink reference signal resource, and the first downlink reference signal resource is a downlink reference signal resource in the first cell or the source BWP.