An approach for low-voltage side reactive power compensators of oil field distribution networks is put forward. The highest investment benefit, which is discounted back to present, is taken as objective function. The restriction of total investment is considered in the form of punishment functions. On the basis of which, an augmented index is established. Every possible installing location of the automatic reactive compensation equipments is regarded as a gene. The value of each gene is the installing time of the corresponding compensation equipment while zero means no compensation equipment needing to install. A genetic algorithm is adopted to determine the optimal dynamic planning results of the compensation equipments on the low voltage side of distribution transformers. The load varying is also considered in the proposed method. Three cases are detailed, such as without limiting total investment, limiting total investment and limiting the investment of every phase showing that the proposed method is feasible.