For analyzing the cost of cultivation and discussing the economic benefit of scallop at different cultivation density, a field experiment of five density groups (10N/layer, 15N/layer, 20N/layer, 25N/layer and 30N/layer) was carried out from May 2013 to April 2014 in the period when scallop grew from 1 year old to the 2 year old,. The results of scallop height on different cultivation denstiy showed that the average shell height of low density cultivation (10N/layer, 15N/layer) was greater than the average shell height of high denstiy cultivation (20N/layer, 25N/layer, 30N/layer), and the cumulative mortility of low denstiy cultivation was lower than the cumulative mortility of high denstiy cultivation (10N/layer<15N/layer, 20N/layer < 25N/layer < 30N/layer). The low denstiy cultivation groups had outstanding advantage on the shell height and reducing mortility of scallop that grew from one year old to two years old. The result of economic benefit showed that in the two economic patterns of fixed number of scallop and fixed number of cultural raft, the economic benefit of 10 N/layer denstiy group was best; the result of experiment showed that low denstiy cultivation of raft cultural scallop had obvious advantage on shell height character and economic benefit. The concept that the higher cultivation denstiy can bring more economic benenfits should be changed, then the mode of ecologic cultivation would be established.