Abstract: SINOPEC Hainan Petrochemical Company was designed to produce the national Ⅲ clean diesel. Due to the high proportion of FCC light cycle oil with very low cetane number in diesel pool, the existing diesel hydrotreating unit with a capacity of 2.0 Mt/a could not satisfy with the production of the national IV or national V diesel. By comparison, a flexible hydro-upgrading MHUG-Ⅱ process with separately feeding system developed by RIPP was selected and adopted for revamping the unit. The results show that the diesel in compliance with the specification of national Ⅳ(S is less than 50 μg/g，cetane number higher than 49) or the national V(S is less than 10 μg/g，cetane number higher than 51) is successfully produced after revamping from mixed feed of straight run gas oil and FCC light cycle oil under mild operating conditions.

Key words: diesel, quality upgrading, flexible hydro-upgrading, unit revamping