As for the problem of low data transfer rate exists in TD-SCDMA, an enhanced system—TD-SCDMA HSDPA is presented. This paper establishes a baseband data flow model for the system terminal, and investigates the system’s throughput and channel outage probability, according to the different modulation schemes and retransmit times. The result shows that the higher the system’s modulation scheme coding rate, the worse the system’s throughput and channel outage probability.