Objective To explore the changes of heart rate (HR) and heart rate variability (HRV) of trainees in the process of fast buoyancy ascent escape training, and to analyze the characteristics of individual stress caused by training, so as to provide scientific basis for effective psychological protection. Methods The electrocardiogram data of 128 officers and soldiers who participated in 3, 5 and 10 m fast buoyancy ascent escape training depths were recorded during the whole process, and the influences of different training phases (before training, during training[cabin entry, cover closing, water injection, cover opening, cabin exit] and after training) and different training depths (3, 5, 10 m) on time domain (standard deviation of normal to normal intervals[SDNN]) and frequency domain (total power[TP], low frequency[LF], high frequency[HF], LF/HF) indexes of HRV and HR were compared. Results The tension of the trainees in the 3 m training depth was significantly higher than that in the 5 m and 10 m training depths (both P<0.01), the tension in the water injection phase was significantly higher than that in the other phases (all P<0.01), and the tension in the cabin exit phase was significantly lower than that in the other phases (all P<0.05). The HR of the trainees increased significantly in the cabin entry phase in the 3 m training depth compared with the 5 m training depth (P<0.05); the HR of the trainees increased gradually after training with the increase of the training depth (P<0.05); and the HR of the trainees in the 3 phases (water injection, cover opening or cabin exit) had no significant difference at each training depth (P>0.05). The indexes of the HRV showed a significant downward trend before, during and after training at each training depth (all P<0.001). Conclusion HR and HRV can reflect the physiological and psychological state of the trainees in the process of fast buoyancy ascent escape training, which provides the basis for stress intervention in the future.