Provided are a method and an apparatus for communication in a TDD (Time Division Duplex) system. A terminal is notified of a change in a first UL-DL setup from a base station during a first change period and receives a second UL-DL setup updated during a second change period. The terminal refreshes a buffer for an ongoing HARQ (Hybrid Automatic Repeat reQuest) process on the basis of the first UL-DL setup according to the reception of the second UL-DL setup.