A differential pressure gauge includes a housing, a leaf spring having a magnetic steel, a measuring diaphragm, a helix, a dial, a range adjusting device and a diaphragm cover. The measuring diaphragm is connected with the leaf spring by connectors. The range adjusting device includes an adjusting spring provided at a lower end of the measuring diaphragm, a balance spring provided at an upper end of the measuring diaphragm, an adjusting screw and a slider which are provided at a lower end of the adjusting spring. The adjusting end of the adjusting screw is provided outside of the housing. The adjusting spring can be compressed by the upper and lower displacement of the slider driven by the adjusting screw, thus affecting the rigidity of the system to change the range of the differential pressure gauge. The differential pressure gauge facilitates adjusting the range and has the accurate measurement.