A diaphragm-type tire pressure indicator is fixedly fastened to the air nozzle of a vehicle tire for indicating a low pressure of the tire. A flexible diaphragm is mounted in a receiving chamber in the casing of the tire pressure indicator. A push rod is connected to the flexible diaphragm for being moved up and down with the diaphragm subject to the status of the tire pressure of the vehicle tire. A sleeve is mounted in the receiving chamber and is around the push rod. A spring is sleeved onto the push rod.