Disclosed is a method for controlling a power level based on a packet error rate (PER) in a wireless personal area network (WPAN) system. The method for controlling a power level based on a packet error rate (PER) in a wireless personal area network (WPAN) system, includes the steps of: a) at a receiver, computing a PER of a packet in an initial check duration of PER (DP) wherein a transmission power level of the packet is set by a piconet coordinator (PNC); b) at the receiver, determining whether the computed PER satisfies a target PER, adjusting a target signal-to-interference ratio (SIR) and requesting a transmitter to adjust the initial transmission power level; and c) at the receiver, determining whether the number (N) of successive G is larger than a power control threshold, wherein G denotes DP satisfying the target PER, changing the target SIR based on the determination result whether the number (N) of successive G is larger than the power control threshold, and requesting the transmitter to adjust the possible transmission power level.