The invention provides a method for preparing potassium formate by means of a membrane method. The method for preparing the potassium formate by means of the membrane method comprises the following steps: (A1) respectively preparing a sodium formate solution and a zinc sulfate solution; (A2) mixing the sodium formate solution and the zinc sulfate solution, and filtering reaction liquid to obtain zinc formate; (A3) preparing a potassium sulfate solution, and preparing a zinc formate solution by using the zinc formate; (A4) mixing the potassium sulfate solution and the zinc formate solution, and enabling the mixed solution to pass through a membrane, wherein monovalent ions in the mixed solution selectively pass through the membrane, and divalent ions in the mixed solution are trapped by the membrane; (A5) concentrating the permeate liquid to obtain a potassium formate solution. The method has the advantages of being low in cost, and the like.