Distributed generation (DG), is the process of generating electricity from many small energy sources and connecting it directly to the distribution network. Determining the optimum location and sizing of distributed generation units is one of the major factors in the distributed network. For maximum power loss reduction, proper positioning and sizing of DG are ardently necessary. In this paper, a heuristic method which employs the plant growth simulation algorithm(PGSA) is proposed to determine the sizing of the distributed generating unit and loss sensitivity factor is used in selection of the optimal location of DG.PGSA is a random search algorithm which is inspired by the growth of the plant. By simulating the growth process of plant phototropism, a probability model is established. Reduction of line losses in the radial distribution network is the main objective of this paper. The proposed method is applied to IEEE 10 bus system and IEEE 33 bus systems. The solution obtained by the proposed method has outperformed in the quality.