The invention discloses a preparation method of a flex-resistant high-airtight rubber material of a vacuum diaphragm, which comprises a proportioning process and a preparing process. The invention adopts the technical scheme that a mixing formula combining ethylene-propylene-diene rubber and halogenated butyl rubber is matched with a corresponding preparation process, thereby overcoming the defects of poor flex resistance and poor air tightness in the prior art. By using the preparation method of the flex-resistant high-airtight rubber material of a vacuum diaphragm, the prepared rubber material which has the advantages of high flex resistance, high fatigue resistance and high air tightness enables the flex resistance and air tightness of a rubber vacuum diaphragm product of an air conditioner throttle of an automobile to be improved.