The increasing proliferation of distributed generations (DGs) in distribution networks has brought several management and operation challenges. To improve energy efficiency and voltage profiles of the distribution grids under different operating conditions, this paper propose a distributed optimal reactive power control solution combined with gradient algorithm. In the proposed method, each DG or reactive power compensation device only needs information measured locally or obtained from its neighboring buses. By utilizing local measurements and communications, the proposed distributed optimization enables the overall network realize the real power loss minimization and the voltage profiles improvement simultaneously. Simulation studies with modified distribution systems demonstrate the effectiveness and superiority of proposed control solution.