In order to shorten the intermediate culture period of razor clam and to quicken the culture of large size products, the suitable specifications and densities of the spat are tested. In November to December 2016, in the 250 m² outdoor large cement pool to cultivate spat, and polyculture of small shrimp, two specifications spat (0.890±0.024 cm, 0.488±0.035 cm) of razor clam S. constricta were cultured with different sediment thickness(3 cm, 6 cm) and density. Regular measuring shell length, shell width, weight and survival rate of spat of razor clam under different conditions, sediment thickness affect the growth of spat in shape, specification, the greater required sediment thickness thicker. The results show that the survival rate of two kinds of specifications of razor clam respectively was 81.83% ±0.69%, 65.74% ±0.83%; stocking density affected the growth speed of spat of razor clam; spat to specifications and the combined effect of rearing density showed that large spat (100,000 grains/kg, shell length 0.890±0.024 cm) appropriate stocking density of 10 000-15 000 grains/m²; small spat (200,000 grains/kg, shell length 0.488±0.035 cm), appropriate stocking density is 30 000-50 000 grains/m²; foster after 30 days, 14.4 kg large-size juveniles harvested 196.4 kg, 96.6% reach (1.5-2.0 cm) commodity seed; 8.8 kg small juveniles harvested seed 144.6 kg, 68.4% reach (1.5-2.0 cm) commodity seed. In this paper, the feasibility of intermediate culture of spat of razor clam in cement pool is explored, shorter intermediate period, it can provid high quality and healthy large specifications spat of razor clam for large-scale and intensive aquaculture.