Regarding the stability of high fill slopes in the construction of mountainous airports, this paper solves the key problems of the finite element strength reduction method of UH (unified hardening) model considering stone content: the determination of the strength reduction parameters, the judgment of the safety stability coefficient and the determination of the initial geo-stress balance method. The Mohr-Coulomb model and the UH model considering stone content are applied to conduct finite element analysis on the stability of high fill slopes in mountainous airports. The comparative analysis is conducted on the slope safety and stability coefficient, displacement, and strain calculated using two models. And the stability laws of high fill slopes are obtained. The effectiveness of applying UH model considering stone content to analyze the stability of high fill slope of airport is indicated.