A compound immunoenhancer for larvae and juvenile of tilapia comprises the following components by weight percent: beta-glucan 20-30, ginsenoside 5-10, seaweed polysaccharides 10-20, phospholipids 5-10, vitamin C-2-polyphosphate ester 20-30, vitamin E 10-15, digestive enzyme 5-10 and citric acid 5-10. The compound immunoenhancer obviously strengthens the immunity of the larvae and juvenile of the tilapia and increases the survival rate, the activities and growth speed of the larvae and juvenile of the tilapia; the compound immunoenhancer is used as a feed additive in the feed of the larvae and juvenile of the tilapia, with additive dosage of only 0.2-0.3%, which has no adverse effect on the feed palatability. The used raw materials enjoy stable sources, low price and simple production technology.