Abstract: An air compressor structure includes a main body, a fixing plate and a cap member. The main body includes a pair of cylinders each having a fixture thereon. The fixture has a pair of first threaded holes. The fixing plate has a pair of second threaded holes corresponding to the first threaded holes. The cap member has a pair of third threaded holes corresponding to the first and second threaded holes. Fasteners are inserted through the first, second and third threaded holes to secure the main body, the fixing plate and the cap member together so as to minimize vibration when the compressor is working and to prevent the compressor from leakage through an air passage and a chamber.