Abstract: The experimental study on critical heat flux of narrow rectangular channel under the condition of single plate heater about upward flow carried on high temperature and high pressures thermal hydraulic test facility was introduced in this paper. The effect of thermal hydraulic parameters such as mass flux and critical quality on CHF in the rectangular channel under the condition of single plate heater had been studied. The results of experimental research showed that: in the range of the test parameters, CHF difference between single plate heater and double plate heater was very little, while effect of quality and mass flux on it was similar. When other parameters kept constant, the CHF of rectangular channel under the condition of single plate heater became lower along with the increasing of critical quality. The CHF became higher along with the increasing of inlet sub-cooling. In the range of lower critical quality, the CHF became higher with the increasing of mass flow flux. However, the opposite trend was observed for higher critical quality. Finally, the formula to predict CHF in rectangular channel under the condition of single plate heater was drawn up, which had perfect results in its prediction scope.