TDD system and its data transmission method

The invention discloses a method for transmitting data of a time division duplex system. The method comprises the following steps: at least a special area configuration is set respectively and correspondingly against an incompatible TD-SCDMA system and a compatible TD-SCDMA system in advance; the special area configuration comprises lengths of a protective gap GP time slot, a DwPTS time slot and a UpPTS time slot with a symbol length as a unit; a base station determines all special area configurations in the corresponding set according to that, at present, whether a compatible TD-SCDMA systemis required or not; and one of all the special area configurations is selected according to current coverage range and system performance requirement, and the selected special area configuration is transmitted to user equipment; the user equipment and the base station construct a wireless frame field for data transmission according to the selected special area configuration. The invention also discloses a time division duplex system. With the adoption of the invention, different rate coverage with finer granularity can be supported, wireless resources are saved, and transmission efficiency isimproved.