The invention discloses a compound irrigation fertilizer for solanaceous vegetables and an applying method thereof. The fertilizer is prepared from the following raw material components in percentage by weight: 30-38 percent of urea, 0-10 percent of monopotassium phosphate, 0-13 percent of potassium nitrate, 10-15 percent of potassium humate, 0-10 percent of magnesium sulfate heptahydrate, 20-40 percent of potassium sulfate, 0-15 percent of monoammonium phosphate, 0.1-0.2 percent of compound sodium nitrophenolate, 0.1-0.3 percent of boric acid, 0.05-0.15 percent of sodium naphthalene acetate and 0.5-2 percent of amino acid chelated zinc, manganese, copper and iron. The fertilizer can fully supply nutrients so as to meet the nutrition requirement on the solanaceous vegetables, and contains humic acid, amino acid, macro elements, medium elements, trace elements and the like. The irrigation fertilizer contains sodium naphthalene acetate serving as a rooting agent and compound sodium nitrophenolate serving as a synergistic agent, so that the root activity can be facilitated, soil is improved, fertilizer absorption is enhanced, and a quick and long fertilizer effect is achieved. High-quality raw materials without irritant odor are selected carefully, precipitates and irritant odor are not produced when the fertilizer is applied along with water, absorption is facilitated, and the utilization ratio of the fertilizer is increased. Prematurity and precocity fruiting of the solanaceous vegetables can be facilitated, reproductive differentiation is accelerated, the commodity value of the solanaceous vegetables is increased, and the yield of the solanaceous vegetables can be increased by 35-35 percent.