Abstract: In order to investigate the fragmentation law of variable wall thickness shell under internal explosive loading, variable wall thickness shells with different taper were designed and experimented with initiation from both ends, explosion in a sand box for recover fragments. Experiment data show that in the case of initiation from the big end, variable wall thickness shell produces more fragments, and larger taper shells have more tension-shear mixing fracture region. After using the Mott distribution to fit and analyze fragments, it shows that in the case of initiation from the big end, the fragments' characteristic mass become smaller. Based on stochastic fracture model of Autodyn software, all the conditions of experiment were simulated, the fragments' cumulative distribution is matching with the experimental results, and the laws of fragments' characteristic mass of Mott fitting among the conditions from simulation are consistent with the experiment results.