The invention relates to a biological pesticide and a method for controlling aphids on eggplant. The biological pesticide is prepared from a garlic and hot pepper water solution which is diluted 50 times with water from the stock solution of garlic and hot pepper water. The stock solution of garlic and hot pepper water is made of stock garlic solution and pepper water with a volume ratio of 1:3~5. The control method is simple, practical and safe, and is of a low production cost and high control effects.
