Abstract: This article introduces the development and application of the medium-pressure hydro-upgrading (MHUG) technology developed by the Research Institute of Petroleum Processing (RIPP). The MHUG technology based on the chemistry of diesel hydro-upgrading reactions has the advantages of flexible product slate and excellent product quality that can increase the cetane rating of diesel fuel up to more than 15 units. The hydrotreating and hydro-upgrading catalysts associated with the MHUG technology have outstanding performance to meet the demand of MHUG technology for hydro-saturation and selective ring-opening of aromatic rings. New MHUG process flow scheme can further increase the yield and selectivity of target products. Commercial application of multiple MHUG units has revealed that the MHUG technology designated for clean diesel production features good feedstock adaptability and operating stability.