Aiming at the fragments of deposit on the fuel cladding caused by the loss of coolant accident of nuclear power stations，a numerical calculation model of the temperature field on the fuel cladding and the coolant is con-structed by using the one-dimensional model． Then，the numerical calculation results are compared with the CFX simulation ones，so as to analyze the influences of the thickness of the dirt，the thermal conductivity of the dirt and the flow rate of the coolant on the temperature rise of the fuel cladding and discuss the transient change of the tem-perature rise． Calculation results show that the numerical results are close to the CFX simulation ones，with a maxi-mum relative deviation of 2%． Through an analysis，it is also found that the dirt deposition leads to a temperature rise on the fuel cladding，and the extent of temperature rise increases with the increase of the dirt thickness as well as with the decrease of the thermal conductivity of the dirt． In addition，it is found that there exists a critical inlet flow rate of coolant，and a boiling crisis occurs in the reactor core when the inlet flow rate of coolant is below the critical value．