Method, network side and user equipment for activating deactivated serving cell

The present invention provides a method for Medium Access Control (MAC) layer to activate the deactivated serving cell in carrier aggregation. The method comprises: the network side maintains the corresponding relationship between each bit of the serving cell information and each serving cell configured for the User Equipment (UE), wherein, during initial configuration the corresponding relationship satisfies an initialization generation principle: each serving cell configured for the UE corresponds to each bit of the serving cell information according to the sequence of component carrier IDentifier (ID), or the sequence of configuration, or the sequence of frequency magnitude; the MAC layer in the network side sends to the UE an operation command and MAC layer control cell of the serving cell which is used for operation, wherein, in the MAC layer control cell, the serving cell indication information is used to indicate the serving cell which is used for operation, and the serving cell corresponding to each bit in the serving cell indication information is in accordance with the serving cell corresponding to each bit in the serving cell information. A network side and UE are also provided in the present invention.