Based on numerical simulation results of three-dimensional two-phase flow field of tail pipe SRM under spinning condition and the extracted ablation boundary parameter, the two-dimensional charring ablation model under spinning condition was established through analyzing the ablation mechanism of insulator. The ablation prediction with different particle diameter and spinning rate was studied. The results show that the ablation position changes evidently under spinning condition and the ablation ratio is enhanced with increasing spinning rate. The insulator ablation in aft closure is caused by highly concentrated particle eroding by spinning.