The manufacture of high-line-density X-ray transmission gratings for X-ray spectroscopy by using electron beam lithography and X-ray lithography was reported. Firstly, a master mask was fabricated on polyimide membrane by electron beam lithography and micro-electroplation. Secondly, X-ray transmission gratings were efficiently replicated by X-ray lithography and micro-electroplating. With the combined technology, 3333 lp/mm X-ray transmission gratings with 300 nm period, 150 nm width of grating bar, and 500 nm thickness of gold absorber, were successfully fabricated in China for the first time. The calibration results of diffraction efficiency show that the fabricated gratings with rectangle cross-section profile and reasonable dispersion and line-and-space ratio, can meet the requirement of X-ray transmission spectroscopy in many fields such as astrophysics, synchrotron radiation facilities and plasma diagnostics, etc.