A method for preparing a pharmaceutical composition for enhancing immunity comprising steps of: mixing ginseng ethanol extract containing total saponins of panax ginseng with fruit and vegetable fermentation conversion solution to obtain a mixture, namely, obtain the pharmaceutical composition for enhancing immunity; wherein the ginseng ethanol extract containing total saponins of panax ginseng is prepared by a following step of: reflux extracting ginseng by ethanol aqueous solution for obtaining the extract, namely, the ginseng ethanol extract containing total saponins of panax ginseng; wherein the fruit and vegetable fermentation conversion solution is prepared by following steps of: mixing the fruit and vegetables: konjak, eggplant, asparagus, spinach, bean sprouts, cauliflower, cabbage, radish, cucumber, pea, cayenne pepper, celery, onion, garlic, grape, grapefruit, watermelon, peach, tangerine, blueberry, sweet orange, banana, litchi, bitter gourd, chinese chive, pomegranate, pitaya, carrot, tomato, chinese cabbage, western celery, sweet pepper, lettuce, pear, ginger, taro, kidney bean, pumpkin, lotus root, cherry, kiwi, smoked plum, strawberry, fig, kumquat, poon kan, southland pear, muskmelon, melon, papaya, onion, mulberry, sugar beet and lemon; lactobacillus acidophilus bacteria solution, bifidobacterium longum bacteria solution, lactobacillus delbrueckii subsp. bulgaricus bacteria solution, streptococcus thermophilus bacteria solution with water, and then fermenting for obtaining a fermentation product, namely, the fruit and vegetable fermentation conversion solution; and wherein the method is characterized in that: in the method, every 1L mixture is prepared by following steps of: mixing the ginseng ethanol extract containing total saponins of panax ginseng with the fruit and vegetable fermentation conversion solution, and complementing a volume by the fruit and vegetable fermentation conversion solution for making a concentration of the total saponins of panax ginseng in the mixture 1.5g/l-50g/l. mixing ginseng ethanol extract containing total saponins of panax ginseng with fruit and vegetable fermentation conversion solution to obtain a mixture, namely, obtain the pharmaceutical composition for enhancing immunity; wherein the ginseng ethanol extract containing total saponins of panax ginseng is prepared by a following step of: reflux extracting ginseng by ethanol aqueous solution for obtaining the extract, namely, the ginseng ethanol extract containing total saponins of panax ginseng; wherein the fruit and vegetable fermentation conversion solution is prepared by following steps of: mixing the fruit and vegetables: konjak, eggplant, asparagus, spinach, bean sprouts, cauliflower, cabbage, radish, cucumber, pea, cayenne pepper, celery, onion, garlic, grape, grapefruit, watermelon, peach, tangerine, blueberry, sweet orange, banana, litchi, bitter gourd, chinese chive, pomegranate, pitaya, carrot, tomato, chinese cabbage, western celery, sweet pepper, lettuce, pear, ginger, taro, kidney bean, pumpkin, lotus root, cherry, kiwi, smoked plum, strawberry, fig, kumquat, poon kan, southland pear, muskmelon, melon, papaya, onion, mulberry, sugar beet and lemon; lactobacillus acidophilus bacteria solution, bifidobacterium longum bacteria solution, lactobacillus delbrueckii subsp. bulgaricus bacteria solution, streptococcus thermophilus bacteria solution with water, and then fermenting for obtaining a fermentation product, namely, the fruit and vegetable fermentation conversion solution; and wherein the method is characterized in that: in the method, every 1L mixture is prepared by following steps of: mixing the ginseng ethanol extract containing total saponins of panax ginseng with the fruit and vegetable fermentation conversion solution, and complementing a volume by the fruit and vegetable fermentation conversion solution for making a concentration of the total saponins of panax ginseng in the mixture 1.5g/l-50g/l.