Abstract: A growth experiment was conducted to evaluate the effects of two sizes of marine sands on the growth and surviva1 rate of Sipunculus nudus L. in intermediate culture stage in 2010 and 2011.The results showed that the larva of Sipunculus nudus L. had a growth advantage and a higher surviva1 rate cultured in marine sand of 250~500 μm than those which cultured in marine sand of 63~250 μm.The results indicated that the size of marine sand was important to improve Sipunculus nudus L's intermediate culture.