Abstract: Reflood process plays an important role in protecting fuel rods from damage and mitigating consequence during loss of coolant accident (LOCA). During the reflood process, the wall temperature drops rapidly, quenching occurs and the heat transfer mechanism changes from film boiling to transition boiling or nucleate boiling after the coolant contacts with the cladding wall. Quench temperature is the main indicator of quenching and the key parameter of the reflood process, which is of great significance to understand the precursory cooling and rapid cooling. Reflooding processes were studied based on doubleside electric heating experimental device, which had a narrow rectangular flow channel in the middle and heating plates on both sides. The size of the rectangular channel was about 2 mm×70 mm×1 000 mm. The initial state was established through the steam circuit including steam boiler, steam preheater, pressure buffer, etc. So that the experimental device was filled with steam. Then heating the experimental device with electricity was started. Until the wall temperature reached the specified value, the cooling water was injected with a certain coolant temperature into the experimental device through the water circuit to simulate the reflood process. The water circuit includes water tank, pump, preheater, flow meter, etc. The outer wall temperature was obtained by means of thermocouples on the heating plates, and then the inner wall temperature was obtained by the reverse thermal conductivity numerical calculation method. Finally the quench temperature was got using double tangent method based on the inner wall temperature. The influence of some thermal parameters on quench temperature were studied including initial wall temperatures, generated power, inlet mass flow flux, inlet coolant temperature and pressure. The results show that the quench temperature is positively correlated with the initial wall temperatures, generated power and pressure，but has no obvious correlation with the inlet mass flow flux and inlet coolant temperature possibly due to doublesided effects. By means of dimensional analysis, 7 dimensionless numbers were obtained and then 5 of them were selected for fitting to get the prediction model of the quenching temperature in the rectangular narrow channel. The applicable working conditions of the prediction model are as follows: pressure 0.10.8 MPa, inlet mass flow flux 230 cm/s, inlet coolant subcooling 2080 ℃, initial wall temperature 400600 ℃, generated power 1.22.4 W/cm2. The results show that 95% of the data is within the ±20% error band of the prediction model.