Abstract: Operation situation awareness and analysis are important measures for weak low voltage distribution grid to prevent meteorological disaster in advance and improve reliability. This paper establishes the impact situation index of disaster on distribution grid, a decision tree and grey correlation method based approach are utilized to solve it. Stochastic Poisson process theory based model is established to calculate the probability distribution of 10kV trolly wire network’s interruption frequency, with reference to the impact situation index under disastrous condition. It quantitatively reflects disaster factors’ impact on the reliability of low voltage distribution grid by way of computing the relative reliability indexes. The work contributes to promotion for city electricity enterprises to improve power supply reliability and construct a strong distribution grid.