A diaphragm pressure gauge generally consists of four parts including a diaphragm part, a movement part, a pointer part as well as an outer cover connection part. The diaphragm pressure gauge uses a diaphragm as the elastic element of the instrument. When the pressure of a medium to be detected acts on the diaphragm, the diaphragm generates a displacement. This displacement is transmitted to the movement part which in turn drives the pointer part to operate, such that the detected pressure is clearly indicated on a dial plate. However, current diaphragm pressure gauges have the following problems. First, the diaphragm is usually made of spring steel (SK5) in order to satisfy the elasticity requirement. The diaphragm made of spring steel gets rusted and corroded easily because of a direct-contact between the structure of the diaphragm and the detection medium (e.g. water or polluted water). Second, there is a large pressure contact area, which requires a large amount of material, a large thickness and strength. These requirements translate into a high cost. Finally, because of the large pressure contact area, this construction is usually suitable only for detecting a low pressure below about 10 kg/cm2 but not suitable for detecting a high pressure such as 1000 kg/cm2.