Abstract: The integration of large-scale distributed generations presents a huge challenge on reactive power optimization for active distribution network. While the traditional centralized control has such disadvantages as being dependent on central control and easy to produce a communication blockage. To improve the control reliability of distribution network, reactive power optimization model is built based on second-order cone relaxation techniques, and a subarea based distributed reactive power optimization control method for active distribution network based on auxiliary problem principle is presented to achieve global active power loss optimization. In addition, border variable standardized method is proposed to improve convergence speed of subarea based reactive optimization. Based on the proposed control method, the reactive power scheduling and global active power loss optimization can be realized just according to the power and voltage information collected from individual partition and interface border variables in neighborhood partitions, which guarantees voltage quality of power system. In the end, by using the IEEE 69-bus distribution system, the effectiveness of the proposed control method is verified by numerical simulations.