—The paper analyzes the relationships among the transmission range, carrier sensing range, and interference range in case that power control is adopted and proposes an adaptive range-based power control (ARPC) MAC protocol for wireless ad hoc networks to avoid collisions. Based on the analysis results, four mechanisms, STRC, RTRC, SCRC, and RCRC are proposed to prevent from collisions. The paper further analyzes the superiority of each mechanism under certain situations and proposes the ARPC MAC protocol to make use of the advantages of the four mechanisms to avoid collisions. The proposed protocol can not only reduce energy consumption of STAs, but also prevent from collisions. Simulation results also verify the advantages of the proposed protocol.