To study the effects of substrate and sowing condition on burrowing behaviors of ark shell Scapharca subcrenata, burrowing processes of ark shell (shell length 10.0 ± 0.9 mm) were observed under laboratory conditions, meanwhile, effects of different substrate grain sizes (251-500 μm and <120 μm) and sowing conditions (centralized and decentralized sowing) on burial time and burrowing rate of ark shell were studied. The results showed that the burrowing behavior of ark shells included three steps: preparation, burrowing and finishing, which could be further divided into six parts inducing closing shell, opening shell, stretching out axe feet, burrowing axe feet into substrate, erecting shell and burrowing shell into substrate, and inhabiting in substrate. In both types of substrates, the burial time required by ark shell under centralized sowing condition was shorter than that under decentralized sowing, but the time differences in both substrates were not significant (P>0.05). While in both centralized and decentralized sowing conditions, the burial time required by ark shell in substrate with grain size 251-500 μm was less than that in the grain size <120 μm substrate, and the time difference between the two types of substrate was significant under the decentralized sowing condition (P<0.05). In both substrate conditions, the burrowing rate of ark shell under centralized sowing condition was higher than that under decentralized sowing condition. Therefore, compared with grain size 251~500 μm, the substrate with grain size of 251-500 μm was more helpful to the burrowing of ark shell, and centralized sowing condition was more favorable to the burrowing of ark shell than the decentralized sowing.