Coke drum is typical industrial equipment which experiences complex thermal and mechanical cyclic load during its operation, and the thermal stress which is produced by the drastic change of temperature is the main cause of the cracking failure of coke drum. This paper aims at coke drum with 1.25Cr–0.5Mo steel, and is based on iterative algorithm. Then we simulate the process of liquid medium climbing the inner surface of coke drum in the stages of oil filling and water quenching with dynamic thermal boundary, and carry out the numerical calculation of transient temperature field of coke drum in main process stages for one operating cycle. After the comparison of simulated temperature values with the measured temperature data at several locations on the outer surface of coke drum, the appropriate equivalent coefficients of convective heat transfer will be obtained. The variation rules of transient temperature field for the key parts of coke drum are discussed. Based on the simulation results of temperature field, the thermal-structure coupling analysis of coke drum is carried out, and the variation characteristics of thermal stress on coke drum are studied later.