In the DSCH power control method for mobile communication system according to the present invention, the cell transmitting DSCH receives a signal from an UE, determines whether a cell transmitting DSCH to be set as primary or non-primary based on the received signal, and controls DSCH transmit power according to a result of the determination. The cell decreases DSCH transmit power when the cell is set as primary and increases DSCH transmit power when the cell is set as non-primary. In the DSCH transmit power control method of the present invention the cell transmitting DSCH sets its state as non-primary when the received signal quality is bad, such that it is possible to prevent the cell transmitting the DSCH from reducing the DSCH transmit power even when the received signal quality is bad, unlike in the typical SSDT.