The invention discloses a cowpea fertigation package fertilizer as well as a preparation method and a fertilizing method thereof, belonging to the technical field of agricultural science fertigation. The fertilizing method disclosed by the invention is characterized by carrying out fertigation by using fertilizers with different nutrient proportions and water with different amounts in three growing periods of cowpea through adopting trickle irrigation equipment, wherein the three growing periods comprise A) a seedling period-flowering period, B) a flowering period-fruiting period and C) a collection period. The fertilizers are obtained by repeatedly preparing the following components of urea, industrial monoammonium phosphate, agricultural monoammonium phosphate, potassium sulfate, ammonium sulfate, ammonium bicarbonate, magnesium sulfate, zinc sulfate, manganese sulfate and the like. According to the fertigation method disclosed by the invention, the use ratio of the fertilizers is increased, the labor intensity is reduced, the economic and social benefits in cowpea cultivation and production are obvious, the effect of increasing yield is good, and the real meaning is great in water-saving agricultural production.