The aim of the study presented here is to compare the pre- and post-operative cardiac autonomic nervous function of senile patients with different functional capacities (FC). Ninety-two senile patients scheduled for elective non-cardiac surgery were selected, whose FC was evaluated in terms of Duke activity status index (DASI). According to FC, the patients were classified into three groups: Group 1 (poor FC); Group 2 (moderate FC) and Group 3 (excellent FC). Heart rate variability (HRV) was monitored during the night before, on the 1st and the 2nd day after operation respectively. The results demonstrated some indices of pre-operative HRV of patients with poor or moderate FC were significantly lower than those with excellent FC. After surgery, total power (TP), high frequency (HF), low frequency (LF) and very low frequency (VLF) of all patients were significantly decreased. The LF/HF of patients with a poor or moderate FC showed a significant difference compared to patients with excellent FC. In conclusion, we emphasize that surgery induced a cardiac autonomic nervous dysfunction in senile patients not only with low FC but also with high FC; the disturbance of pre- and post-operative cardiac autonomic nervous activity is associated with a diminished FC (<7METs=metabolic equivalents) in senile patients.