This paper proposes a reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy is based on constant DC capacitor voltage control, which is always used in active power line conditioners. Therefore, the proposed reactive power control strategy does not require active, reactive calculation blocks of load currents for the reference source current calculation. Balanced source currents with a predefined power factor can be achieved without unbalanced active and reactive components detection of the load currents. The basic principle of the reactive power control strategy for the ALB is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested to validate the feasibility of the proposed control algorithm. Simulation and experimental results demonstrate that balanced source currents with a predefined power factor are achieved in three-phase four-wire distribution systems.