The purpose of this study is to investigate the relationship between physical efficiency index (PEI) calculated by the Harvard step test and heart rate variation (HRV), and to identify parameters of HRV that can predict PEI in college students. Sixteen college students were partici-pated in this study and they were randomly divided into two groups; higher PEI group (HPEI, n=6) and lower PEI group (LPEI, n=10). To in-vestigate the relationship between PEI and HRV, we were measured HRV and Harvard step test. HRV test was the resting, immediately, 15 min and 30 min after the Harvard step test using electrocardiography device polyG-I. Relationship between PEI and HRV were determined Pearson correlation coefficient, and multiple regression analysis was performed for examining HRV parameters to predict PEI. As shown in the result, not only PEI was negatively correlated with root mean squared differences between adjacent normal RR intervals (RMSSD), but had a positive correlation with low-frequency/high-frequency, but also normalized low frequency (normLF), the ratio of LF, and RMSSD, the change in RR interval showed a significant difference at each time point of measurement according to PEI levels. But, there were no sig-nificant differences among the HRV variables except normLF and RMS-SD. Our findings suggest a critical information that PEI calculated by the Harvard step test can be used as an index to predict the autonomic nerve function, and high PEI may have a positive effect on changes in autonomic nerve activity during recovery after exercise intervention.