The invention discloses a digital predistortion method and a device for a TD-SCDMA system. the method of the invention comprises the following steps that: step 1. when the current time slot signal is a downlink time slot and a DPD module is started, setting a counting threshold and an average power threshold of a counter; step 2. selecting medium frequency feedback data of m symbols from the data area of the current downlink time slot, and computing to obtain the average power of time slot signals; and step 3. by judging the average power or counting number of times of the time slot signals obtained by sampling and computing of a medium frequency feedback signal part interval, finding the medium frequency feedback data required to be sampled, and simultaneously discarding the medium frequency feedback data not required to be sampled, thereby avoiding carrying out continual searching, collection and parameter estimation on all medium frequency feedback data in a feedback channel, notably reducing the computing capacity of the DPD module, saving the computing time and reducing power consumption of devices.