We performed experiments at stocking densities of 2, 5, 8, 14, and 20 larvae/mL to determine optimallarval density for hatchery culture of bloody clam, Scapharca subcrenata. Larval developmental stages fromD-veliger to settlement and metamorphosis were included. The results indicated that total ammonia nitrogen (TAN)and nitrite increased significantly with increasing stocking density (P<0.05). TAN and nitrite levels in the 20 larvae/mL group reached maximum values of 0.089 mg/L and 0.008 mg/L, respectively. Dissolved oxygen (DO)concentrations decreased significantly with increasing stocking density (P<0.05), and DO concentrations in the14- and 20-larvae/mL groups were lower than those in the other treatments. Larval growth decreased significantlywith increasing stocking density (P<0.05). A density of 5–8 larvae/mL appeared to be optimal for normal S. subcrenatagrowth. Larval survival rate decreased with increased stocking density, and survival rate was 35% in the20 larvae/mL group(P<0.05). Larvae reared at 8 larvae/mL exhibited comparatively higher settlement density thanthat of the other stocking density groups(P<0.05). Comparatively higher settlement density was observed on thelower substrate layer than that on the upper and middle layers (P<0.05). Settlement time was prolonged and thesize of the settled larvae decreased as stocking density increased (P<0.05). Therefore, a stocking density of 5–8larvae/mL is recommended for large-scale seed production.