Abstract: Factors influencing the daily dynamics of pod dehiscence in Vicia cracca were investigated on both sunny and cloudy days to find when the pods dehiscence and the relationships between pod dehiscence and environmental conditions. The results showed that the pod dehiscence rate had a significant positive correlation with air temperature, humidity, pod wall temperature, and moisture content on sunny days (P<0.01). On cloudy days, such factors, but not pod moisture content or wind speed, had a significant correlation (P<0.05) with pod dehiscence. Peak pod dehiscence occurred at 12:00 to 14:00 and there was little dehiscence before 8:00 or after 18:00. More pods dehisced on sunny days than on cloudy days. These results indicate that pod dehiscence rate is closely correlated with air temperature and humidity. To reduce seed loss, the optimum harvest time is in the morning before 8:00 or at dusk after 18:00.