This study simulates the soils with spatial variability by random field theory and Karhunen-Loeve ex? pansion. Reliability analysis of strip footing lying on karst area is carried out based on finite element limit analysis and Monte Carlo simulation. The emphasis of this study is performing the parametric analysis through finite element modeling，in order to explore the effect of karst cave parameters（including depth and horizontal offset distance of karst caves）and spatial variability parameters（including correlation length and coefficient of variation）on the ulti? mate bearing capacity and failure probability of footings. Then，combined with the visualization of failure patterns of cave-footing system，the variation mechanism of footing failure probability is revealed. Finally，the finite element analysis results are compared with the existing research results to verify the accuracy of the numerical model and the reliability of the research conclusions. The results indicate that the higher the disperse degree of failure curve is，the more failure paths may develop under external loads，which leads to a higher failure probability of the footing. Fur? thermore，the footing failure probability increases with the increase of distance between the karst cave and the footing. The higher spatially variability of soils also leads to a higher failure probability of the footing. And the failure probability decreases significantly with the increasing factor of safety. If the method proposed in this paper is used for reliability analysis in the advanced design，the safety factor should be larger than 2 as far as possible and the lower limit theory should be used for analysis，in order to guarantee the safety.