Abstract: An experimental study was carried out to investigate the critical heat flux （CHF） during natural convective boiling in the inclined annular tube with a heated inner tube submerged in both saturated liquids of water and R-11 under atmospheric pressure. The experimental results show that the CHF decreases with increasing the ratio of the effective heated length to the tube gap, while the CHF decreases with decreasing the inclination angles. A semi-theoretical correlation using for the CHF during natural convective boiling in the vertical annular tube was modified. The modified correlation can reasonably well predict the CHF for the inclined annular tube. The correlation was also compared with the CHF data of the inclined annular tube from other literature.