The invention provides cooking flavor green Chinese onion powder and a preparation method thereof. The cooking flavor green Chinese onion powder comprises the following raw materials in part by weight: 30 to 50 parts of green Chinese onion, 30 to 50 parts of green Chinese onion powder, 50 to 100 parts of onion concentrated juice, 5 to 10 parts of spice powder, 0.1 to 0.3 part of cellulase, 10 to 20 parts of malt dextrin, 5 to 20 parts of edible oil, 50 to 100 parts of water, 0.01 to 0.05 part of butylated hydroxyanisole and 0.5 to 1 part of xanthan gum. The cooking flavor green Chinese onion powder is prepared by steps of pulping, enzymolysis, stirring, heating, homogenizing, sieving and spray drying; and the prepared cooking flavor green Chinese onion powder has strong taste, has the green Chinese onion taste formed by cooking in kitchens, is unique in flavor and convenient to store, carry and use, is particularly suitable to be used as seasonings for instant noodles, puffed food, nutrition conditioning food, meat products and food beverages, has the advantages of high quality of finished products, low production cost and the like, and is easy to prepare.