The invention relates to an amoxicillin sodium potassium clavulanate preparation for injection and a preparation method of the preparation. The preparation consists of an amoxicillin sodium crystal and potassium clavulanate at mass ratio of (5-10) to 1, wherein the grain size of the amoxicillin sodium crystal is 25-35microns. The preparation method comprises the following steps: preparing the amoxicillin sodium crystal, uniformly mixing the amoxicillin sodium crystal and the potassium clavulanate according to a fixed mass ratio, and packaging an obtained mixture in a small bottle of 25ml so as to obtain amoxicillin sodium potassium clavulanate powder for injection; and in the clinical field, on the basis of a dispensing scheme of dissolving the powder in 20ml of injection water, an amoxicillin sodium potassium clavulanate injection solution is obtained. The amoxicillin sodium crystal disclosed by the invention is high in purity and low in content of impurities; and the amoxicillin sodium potassium clavulanate preparation for injection is good in stability and is not easy for causing allergy.