In the process of graphite mining, due to the poor stability of graphite surrounding rock, it has brought great threat to the safety production of the mine. In view of the current situation that the spatial variability of rock mass mechanical parameters was not considered in the calculation of the instability probability of graphite ore by the existing response surface method. Firstly, based on the mathematical logic of the combination of variogram and covariance function, the correlation among variables was analyzed, and a regionalized cross-correlation random field that can reflect the spatial variability of rock mass parameters was constructed. Then, combined with the failure proximity index, the limit state equation of fractured rock mass instability was constructed. Finally, the response surface method was used to analyze the failure probability of the goaf, and the quantitative evaluation of instability risk of graphite mine goaf considering parameter spatial variation structure and response surface method was realized. The results show that the instability probability of the two sides calculated by the Monte Carlo method is 17.67%, and the instability probability of the roof is 30.19%. The instability probability of the two sides calculated by the response surface method is 17.71%, and the instability probability of the roof is 29.57%. The response surface method only uses Monte Carlo method to calculate 1/4 of the time to obtain a more accurate reliability calculation result, which simplifies the calculation process and improves the calculation efficiency.