A power control method performing a power control operation between a radio network controller and a node B is provided. The method includes steps of: calculating a packet error rate threshold and a base received packet count according to a target block error rate (BLER) and a precision of the target BLER; obtaining an accumulated received packet count and an accumulated packet error count; increasing a target signal-to-interference ratio (SIR) of the node B when the accumulated packet error count is greater than a product of the accumulated received packet count and the packet error rate threshold; decreasing the target SIR when the accumulated received packet count is greater than or equal to a product of the base received packet count and a threshold parameter; and resetting the accumulated received packet count and the accumulated packet error count after the target SIR is adjusted.