Reciprocity has become one of the most prevalent social norms and plays a very important role in economic and social activities. Especially in the face of today's risk society, technological means such as mobile communication and online platforms have enabled online reciprocal mutual aid behaviors to cross physical space and establish online group reciprocal communities. We use mutual aid data from China's largest online community of truck drivers over a three-year period to discuss the mechanism of the effect of different dimensions of psychological distance on reciprocal behavior at different levels of risk heterogeneity in risky contexts through quantile regression, and further consider the differences in the effects of two different contexts, emergency and non-emergency. It was found that geographic distance based on urban community labeling and social distance based on risk category similarity were closer to promote reciprocal behavior; the effect of temporal distance on reciprocal behavior showed an inverted U-shaped characteristic; and the hypothetical distance based on variability of disaster degree produced different directions of action in different contexts. This study adds to our understanding of group boundary distance and the mechanisms of reciprocity generation in risky help-seeking scenarios.