Abstract: At present, the basic reserve fund calculation method of power grid construction project is mainly based on a fixed rate. However, the basic reserve fund is to deal with the unexpected expenses, it has the characteristic of uncertainty, and cannot reflect the real situation of basic reserve fund though a fixed rate. Therefore, the distribution fitting of influence factors to basic reserve fund calculation were analyzed by Minitab, including change factor, natural disaster factor and extra building cost factor. Then a calculation model was established according to the relationship among the factors. Finally, combined with an actual case, the value of basic reserve fund was calculated by Monte Carlo simulation （MCS） on Matlab. The simulation results show that this calculation method can well reflect the accurate changes of basic reserve fund in actual works, compared with the existing calculation methods, which can provide a reference for related cost personnel to control project cost reasonable

Key words: basic reserve fund calculation, Monte Carlo simulation, influence factors, distribution fitting