The impact of Kuroshio warm tongue in the East China Sea on the intensity of Tropical Cyclone (TC) Prapiroon (1807) is analyzed by performing a set of numerical experiments using the Weather Research and Forecasting (WRF) model. The results suggest that the high sea surface temperature of the Kuroshio warm tongue leads to the significant increase of heat flux at the air-sea interface under the TC, and causes the development of instability characteristics in the TC boundary layer, forming a boundary layer environment conducive to the development of vertical convection. Therefore, the convection in the TC, especially in the TC eyewall, is more active, and the TC intensity is significantly increased. The local heating of TC by Kuroshio warm tongue also causes the asymmetric distribution of convections in the TC. According to the results of numerical experiments, the Kuroshio warm tongue contributes about 24.7% to the total kinetic energy of Prapiroon, and the response time of central pressure change to the high sea surface temperature of Kuroshio warm tongue is about 10 h. In addition, under the effect of Kuroshio warm tongue, the radius of moderate gale of Prapiroon expands by 16.3%, and the radius of maximum wind shrinks by 10.7%.