Since the 13th five-year plan, the Beijing-Tianjin-Hebei region has vigorously promoted the policy of "coal-to-electricity" and steadily promoted the process of electric energy substitution. With the increase of electricity load, how to carry out reconstruction and expansion planning of rural low-voltage distribution network becomes a problem. Considering distribution transformer cost, distribution line cost and system line loss cost, a distribution network expansion planning model based on life cycle cost is established and solved by genetic algorithm. According to the characteristics of distribution network planning model, a strategy based 〖JP4〗on real number coding is designed to improve the efficiency of parallel solution generation. Finally, an actual rural distribution network planning is taken as an example to verify the results. The results show that the proposed method achieves the life cycle economic optimization of the planning scheme on the premise of meeting the demand of coal-to-electricity load.