We have attempt to use aerostatic guideway to load the diamond carriage system in large diffraction grating ruling engine. Aerostatic guideway undertakes the task of bearing and guiding the diamond carriage system simultaneously. Applying air as lubricant, the friction of aerostatic guideway is approach to zero and can avoid the wear and creeping phenomenon. The motion error of the aerostatic guideway as well as the error′s influence on the diamond carriage system are analyzed. The linear movement accuracy of diamond carriage system during the ruling process is measured with a dual-frequency laser interferometer. The results show that the linear accuracy is about 200 nm on 400 mm one-way trip, less than using quartz guide. Besides, there is a significant improvement in high frequency vibration. An echelle grating with 79 gr/mm and 400 mm×500 mm area has been ruled by this system. The grating′s diffraction spot is displayed and its stray light intensity varies from 0.2‰ to 5‰ in different positions, examining with an illuminometer. The results show that the aerostatic guideway can satisfy the requirements of grating ruling.