The invention relates to a fish feed and a preparation method thereof, in particular to a grouper compound feed and a preparation method thereof. The grouper compound feed consists of the following raw materials in percentage by mass: 30 to 40 percent of fish meal, 15 to 20 percent of bean pulp, 10 to 20 percent of wheat high protein flour, 20 to 30 percent of flour, 1 to 2 percent of yeast powder, 1 to 2 percent of compound vitamin, 0.1 to 1 percent of compound mineral matter, 0.5 to 1 percent of choline, 1 to 2 percent of monocalcium phosphate, 2 to 4 percent of isinglass, 0.1 to 0.5 percent of VC and 1 to 2 percent of dried small shrimp powder. The feed of the invention is prepared by refining according to the growth characteristic and nutritional requirement of the groupers, has comprehensive nutrition and strong food calling property, can furthest release the growth potential of the groupers, adds various mineral matters and vitamins and can improve the gut immunologic barrier and strengthen the immunologic function.