The disclosure discloses a method for sending a Hybrid Automatic Repeat Request Acknowledgement (HARQ-ACK) message in a Time Division Duplex (TDD) system and a User Equipment (UE), in order that the UE feeds back the HARQ-ACK message of each downlink serving cell and downlink subframe in Physical Uplink Control Channel (PUCCH) format 1b with channel selection in the TDD system. When there are more than 1 downlink subframes in a downlink subframe window corresponding to an uplink subframe, the feedback mode when the UE feeds back the HARQ-ACK message in format 1b with channel selection is determined through the configuration of the high layer or according to the result about whether the UE receives the Physical Downlink Shared Channel (PDSCH) from a secondary downlink serving cell. In feedback mode 1, the UE adopts the mapping table defined by Long Term Evolution Advanced (LTE-A) (Rel-10), generates the HARQ-ACK message in the mapping table by a time domain bundling method, and determines the corresponding PUCCH resources in the mapping table by a preset new PUCCH resource determining method.