The invention provides a bath solution supplementing method for a microarc oxidation ion exchange membrane electrolytic bath. The method comprises the following steps of: measuring the content of hydroxide in solution in a cathode chamber; according to the measured content of the hydroxide, the quantity of microarc oxidation solution to be supplemented and the content of initial hydroxide in the microarc oxidation solution, transferring a certain volume of solution in the cathode chamber into a microarc oxidation solution supplementing bath; calculating the using amounts of other additives in the microarc oxidation solution to be supplemented, adding the additives into the supplementing bath and sufficiently stirring to ensure the additives to be dissolved; adding purified water, diluting to ensure the content of the hydroxide and the content of other additives to reach the initial content of microarc oxidation electrolyte to obtain supplemented solution; adding the regulated supplemented solution into an anode chamber of the electrolytic bath, controlling the flow of the supplemented solution and measuring the pH value of the supplemented solution so as to ensure the pH value of the supplemented solution in the initial pH value range; and after carrying out circular stirring on the solution in the anode chamber, normally carrying out microarc oxidation operation.