The addition of new units is estimated to cost around CNY7bn ($1.1bn).
The company is installing new units including hydro treaters for gasoline and diesel to allow the refinery to process the sour-crude grades.
The Qinzhou plant with a capacity to process 200,000 barrel-a-day started operating last year and was originally designed to process Sudan crude, a lower- sulfur grade.
It currently processes more than ten grades of low-sulfur oil.
Construction of the new units is expected to be complete by the end of 2012, reports Bloomberg.
