OBJECTIVE: To study the pilots\' heart rate variability (HRV) characteristic before, during and after parallel swing and the possibility of evaluating vestibule-vegetative nervous reaction under linear acceleration. METHOD: 37 healthy male pilots participated in parallel swing test. Dynamic ECG was recorded for 15 min before, during and after swing, using model MR-4500 Holter recorder. All spectra were estimated from 15 min HRV by autoregressive (AR) modeling method, the model order (8-15) was chosen using automatic program. The ratio of lower-frequency (LF) to high-frequency (HF) power of HRV spectrum (LF/HF) was computed. The relation between change of those ratios in different swing stage and swing time was analysed. RESULT: Ratio of LF to HF during swing was markedly lower than those of before and after swing (P<0.01). CONCLUSION: The vagal nervous activity was markedly increased during swing. There were complexity and versatility in the heart automatic nervous regulation before, during and after swing.