Abstract: Critical heat flux (CHF) is an important parameter for pool boiling, which determines the popularization and application of heat transfer devices. The surface roughness and saturated pressure have significant effects on the distribution of heat transfer boundary layer, the ability of working liquid spreading and dynamic properties, so that have a major impact on CHF of pool boiling. An experimental visualization and heat transfer study on CHF of HFE-7100 as working fluid on copper surfaces with various surface roughnesses (0.019, 0.205, 0.311 and 0.587 μm) under different pressures (0.07, 0.10, 0.15 and 0.20 MPa) has been conducted. The effect of surface roughness and pressure on CHF of pool boiling was analyzed, and the accuracy of CHF predictive model was also compared. The visualization results show that two-phase working fluid at boiling critical state is composed of small bubbles, large bubbles, vapour column and mushroom vapour, while non-flat vapour film at transitional state will cover the surface and inject bubbles. It also can be found that both surface roughness and saturated pressure can enhance CHF of pool boiling. Compared with other predictive models, CHF correlation of Bailey et al. can predict the critical boiling heat flux of HFE-7100 relatively accurately. To further improve the prediction accuracy, the new empirical correlation for CHF dimensionless K was developed. The predicted results are in good agreement with our and other literatures’ experimental data.