Abstract: Under the condition of a onesided heating flux, an experimental research on the enhanced heat transfer characteristics of the subcooled flow boiling for the fusion reactor divertor was carried out. Deionized water was used as the experimental medium. The compound heat transfer tube was designed by using the synergistic enhanced heat transfer effects of the internal thread tubes and twisted tape inserts. The experimental parameters are as follows: mass fluxes from 992 kg/(m2·s) to 4 960 kg/(m2·s), pressures from 0.4 MPa to 2 MPa, inlet subcoolings from 87.01 ℃ to 119.21 ℃, and heat fluxes from 1 MW/m2 to 16.3 MW/m2. The heat transfer characteristics and performance evaluation criteria (PEC) were compared and studied for the four kinds of enhanced heat transfer tubes (plain tubes, tubes with twisted tape inserts, internal thread tubes and compound heat transfer tubes). The results show that: Compared with the other three kinds of tubes, the heat transfer coefficient and PEC of the compound heat transfer tubes are the highest, and the heat transfer characteristics are the best. Within the range of experimental conditions, the heat transfer coefficient of the compound heat transfer tubes is about 5%98%, 99%102% and 179%184% higher than that of the internal thread tubes, tubes with twisted tape inserts and plain tubes, while the overall PEC of the compound heat transfer tubes varies between 0.911.41. Then, the influences of the twist ratios, pitches, pressures and mass fluxes on the heat transfer coefficient for the compound heat transfer tubes in the twophase flow boiling were also conducted. It is found that the heat transfer coefficient is directly proportional to the pitches and mass fluxes, and inversely proportional to the twist ratios and the pressures. In addition, according to the experimental data, the wall superheat temperature and heat flux at ONB point increase with mass flux, which indicates that the larger mass flux can postpone the generation of ONB point. Finally, the four existing empirical correlations for subcooled flow boiling heat transfer were compared and evaluated. Based on the dimensionless models and the nonlinear fitting method, the Nusselt number correlation modified by adding the twist ratios and ratio of the pitches to the hydraulic diameter of the tube (t/Dh) for the compound heat transfer tubes in the subcooled flow boiling is proposed. It is found that the deviation between predicted values and experimental values is within ±15%, the new correlation has a MAE of 5.69% and a RMSE of 7.55%, respectively. Therefore, it is indicated that the new developed correlation has the excellent agreement and effectiveness to predict the values for the compound heat transfer tubes.