For supplying reactive power in order to decrease power loss, capacitors equipped distribution systems are used. This paper presents an efficient optimization algorithm named oppositional krill herd (OKH) algorithm for selecting the installation locations of the capacitors to reduce power loss considering different constraints in radial distribution system. To prove the feasibility and superiority of the planned OKH algorithm, 34-bus and 69-bus radial distribution systems are used as test studies and the obtained results are compared with other reported methods. Comparison study with other reported method demonstrate the fact that the proposed method gains upper hand in solving optimum capacitor planning problem in radial distribution system.