Infauna have developed physiological and behavioral strategies to cope with the stresses of sedimentary environments. Of the two, behavioral strategies are more important because they create microenvironments in the burrows which are essential for the survival of burrowing benthic animals. However, the few relevant published studies have not clarified the relationship between behavioral strategies and the microenvironment of benthic animal burrows. In the present study, we used a behavioral observation device to study the effects of temperature (15 ℃, 20 ℃, and 25 ℃) and body size [large size (2.2±0.2) g, medium size (1.5±0.2) g, and small size (0.7± 0.2) g] on the behavior of Perinereis aibuhitensis in the burrow. We also investigated the water exchange, nutrients, and dissolved oxygen in the burrow. The results showed that temperature had a significant effect on the radial undulating frequency of P. aibuhitensis (P＜0.05), which increased with increasing temperature. Further, body size had a significant effect on the axial crawling velocity of P. aibuhitensis (P＜0.05). The axial crawling velocity of large P. aibuhitensis decreased with increases in temperature, whereas the axial crawling velocity of medium and small P. aibuhitensis increased with increasing temperature. The temperature and body size had no significant effect on the radial undulating and axial crawling duration (P＞0.05); however, body size had significant effects on the pumping volume, pumping rate, and nutrient dissolving efficiency (P＜0.05). The pumping volume and nutrient dissolving efficiency increased with increases in body size. Moreover, the maximum pumping volume of P. aibuhitensis was 10.01 L/d in the group of large individuals and the maximum dissolution efficiency of phosphate, nitrite, ammonia nitrogen, and sulfide in the burrow were 109.80 μg/cm² /d, 6.02 μg/cm² /d, 60.56 μg/cm² /d, and 15.40 μg/cm² /d, respectively. Radial undulating motion is the main action in moving and pumping. The dissolved oxygen threshold of pumping behavior in P. aibuhitensis is consistent with optimality theory, which is designated the “optimal dissolved oxygen obtainment strategy” in this study. It showed an upward trend with increases in temperature and body size. This study showed that small P. aibuhitensis individuals moved more actively than large ones at high temperatures or under low dissolved oxygen levels, indicating that they might have a higher tolerance for these conditions. The large P. aibuhitensis individuals showed a superior ability for bioirrigation at high temperatures. It was likely that dissolved oxygen in the burrow was the key factor driving the initiation of pumping. The release of nutrients from sediment is an additional effect resulting from the polychaetes pumping water to get sufficient oxygen.