For large-aperture optical/infrared astronomical telescopes, mirror coating is one of the most important maintenance technologies to ensure their stable and efficient operation. The quality of the coating directly affects the optical reflectivity of the mirror, and further the imaging quality and observation efficiency (throughput) of the astronomical telescope. LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope), the first astronomical national major scientific and technological infrastructure, has passed the national completion acceptance and gradually put into survey observation since June 2009. At present, it has entered the second five-year regular sky survey stage, and already acquired about twenty million spectral products and achieved a lot of important scientific discoveries. LAMOST has 24 Schmidt corrector (MA) sub-mirrors and 37 spherical primary (MB) sub-mirrors. In order to maintain LAMOST mirror reflectivity and further LAMOST spectral efficiency at the highest level in the wild observatory environment, all sub-mirrors are re-coated every year or every two years. This paper mainly introduces the LAMOST coating requirements and actual implementation progress of the latest coating technology optimization. Based on a lot of experiments and improvements, a set of feasible coating process is finally explored and mastered during the past ten years with the optimal quality of the LAMOST sub-mirror coating. The average reflectivity of all the sub-mirrors over the visible waveband after coating is more than 90%, which satisfies the requirements of the mirror reflectivity of LAMOST spectroscopic survey.