The present invention discloses a power control method, a power control system and a related device. The method includes: monitoring a downlink data sending condition of a dedicated physical data channel (DPDCH), and if no downlink data is sent on the DPDCH, determining to decrease downlink transmit power of a DPCH, or if downlink data is sent on the DPDCH, determining to increase or maintain downlink transmit power of a DPCH. The present invention can reduce the downlink transmit power of the DPCH and promote experience of other users on a precondition of ensuring system performance.