The utility model discloses a fastening structure of a fuel injector, which comprises a fuel injector sleeve arranged on a cylinder cover and a camshaft frame fixed on the cylinder cover, wherein the bottom of the fuel injector sleeve is fixed on the cylinder cover, and the top portion of the fuel injection sleeve is matched with the camshaft frame, a fuel injector is arranged in the fuel injector sleeve, and is connected with the camshaft frame through a fastening turnbuckle. The fastening structure makes structure simple and reliable and has excellent assembly technology, aiming to the disadvantages of complicated connecting structure of an fuel injector and the cylinder cover, high difficulty of processing technology and high cost in the prior art. As the whole fuel injector mounting hole is unnecessary to cast on the cylinder cover, the mode of the cylinder cover can be simplified, and the processing technology of the cylinder cover can be optimized, thereby reducing production cost, and being beneficial for maintenance. The fastening structure can be widely applied in engines which adopt four-valve double-overhead camshaft structures.