Objective To study the application of heart rate(HR) and rating of perceived exertion(RPE) scale in monitoring the physical fatigue in the divers during the 100 msw heliox saturation diving. Methods The 100 msw pressure environment was simulated by a 500 msw saturation diving system: pressure was 1.1 MPa; oxygen partial pressure was 35-52 kPa; carbon dioxide partial pressure was <0.5 kPa;the temperature during exposure to high pressure was (31.0±1.7)℃;and the relative humidity was (76.8±3.5)%. Respiratory gas was heliox. The 18 divers' HR and the scores of RPE scale were recorded at 6 time points, including (1)the day before the subjects entered the chamber; (2) the first day that the subjects were exposed to 100 msw pressure environment; (3) the peak of the subject physical exercise load test under 100 msw pressure environment; (4) the second day under 100 msw pressure environment; (5) the first day that the subjects were out of the chamber; and (6) the seventh day that the subjects were out of the chamber. All the data were analyzed with paired-samples t-test. The correlation was analyzed with Pearson correlation. Results From the day before the subjects entered the chamber to the first day that the subjects were exposed to 100 msw pressure environment, the resting HR of subjects was significantly decreased (P<0.05); From the first day that the subjects were out of the chamber to the seventh day that the subjects were out of the chamber, the resting HR was significantly increased (P<0.05). Significant differences were also found in the basic RPE score of the subjectes between before entering the chamber and after entering the chamber(P<0.05). During the 100 msw heliox saturation, with the variable physical work loads, the trend of of heart rate changes was still in accordance with the score of RPE scale, with that measured at the peak of the subject physical exercise load test under 100 msw pressure being significantly different from that measured at the first day the subjects were exposed to 100msw pressure (P<0.05).The RPE score was significantly related with the HR of divers (r=0.734, P<0.01). Conclusion The combined application of HR and RPE scale can monitor the physical fatigue of the divers during 100msw heliox saturation diving.