There is uncertainty during analysis the stability of karst roof under pile tip. The interval numbers are used to express the calculation parameters. Secondly, the limit equilibrium analysis model of karst roof under pile tip is presented based on the present study. Thirdly, the performance function is suggested to evaluate the reliability of the stability of karst roof under pile tip. The non-probabilistic reliability analysis method for stability of karst roof under pile tip is finally founded. This method is proved to be rational and feasible by engineering case analysis.