Based on the bag-sealed pile formation test and four sets of indoor static load tests，combined with seven sets of numerical models，the feasibility of pile formation，pile load transfer characteristics and load-bearing mechanism of bag-sealed piles were studied. The research results show that：1）The bag-sealed pile has the charac teristics of good pile quality and predictable pile shape while solving the problem of slurry leakage during pile forma? tion in karst areas. Under the conditions of equal pile diameter and equal loading，the ultimate bearing capacity of the bag-sealed pile is more than 1.15 times that of the traditional pile，the settlement of the pile top is much smaller than that of the traditional pile；and the settlement of the pile top is much smaller than that of the latter. 2）When the bag-sealed pile is loaded，each pile section plays in turn from top to bottom and carries the load alternately. The en? hancement of the end-bearing effect of the branched section on the load bearing capacity is greater than the weaken? ing of the bag on the side friction resistance，which is the load-bearing characteristics of the bag-sealed pile. 3）The branched section enhances the pile-rock bonding capacity，in which the lower part of the branched section plays the main bearing role and the upper part only plays the structural role. 4）The asymmetric distribution of the branched sections is one of the unfavorable factors for load bearing，which puts forward a requirement for the design of the bending resistance of the bag-sealed pile. The experimental and numerical simulation results demonstrate the pile formation process of the bag-sealed pile，reveal its unique bearing mechanism and verify its superiority of bearing performance. The research findings can provide ideas and bases for the application of bag-sealed piles in karst areas.