The invention relates to compound sinking soft pellet diet suitable for seahorse breeding in circulating water. The soft pellet diet consists of the following components in percentage by mass: 33 to 36 percent of fish meal, 22 to 23.8 percent of high-gluten flour, 7 to 8 percent of puffed soybeans, 4 to 5 percent of corn protein powder, 2.5 to 3.5 percent of a mixture of soybean oil and fish oil,13.5 to 16 percent of soybean meal, 1.5 to 3 percent of spray-dried animal blood cells, 0 to 6.5 percent of fine rice bran, 3 percent of meat powder, 2 percent of soybean lecithin, 2 percent of calcium dihydrogen phosphate, 2 percent of zeolite powder, 0.5 percent of a vitamin premix, 0.5 percent of a mineral premix, 0.3 percent of choline chloride, and 0.2 percent of xanthophyll. According to theinvention, the compound soft pellet diet overcomes the defects of traditional methods of breeding seahorses by using fresh or frozen opossum shrimps and fairy shrimps, reduces the invasion probability of causal organisms, and improves the survival rate of bred seahorses.