The invention discloses iron-dextrin injection liquid for tonifying qi-blood and used for animals. The liquid is prepared from, 5-15% w/v of iron-dextrin by iron, 1-3% w/v of radix codcnopsitis pilosulas extract, 1-3% w/v of astragalus polysaccharides, 0.003-0.008% w/v of vitamin B12, 0.003-0.008% w/v of folic acid, 1-3% w/v of vitamin E, 0.05-0.1% w/v of sodium selenite, 0.2-5% w/v of Twain-80 and the balance injection water; dextran in iron-dextrin is formed by mixing dextran with the weight average molecular weight of 5,000-6,000 Da, 6,000-6,500 Da and 6,500-7,500 Da. A preparation method of the iron-dextrin injection liquid comprises the steps that the set amount of Twain-80, folic acid and vitamin E are added to a container and evenly mixed, and then hot injection water with the amount of 10% of the total amount is added for dissolution; vitamin B12, sodium selenite, radix codcnopsitis pilosulas extract and astragalus polysaccharides are added and stirred and dissolved to obtain amixture; set iron-dextrin is added to the mixture and evenly stirred, and the injection water continues to be added. The iron-dextrin injection liquid has definite treatment effects on pregnant sowsand piglets and is worthy of popularization.