Abstract: This unique process is a feed forward control of hydroprocessing by on-line sulfur speciation. An on-line gas analyzer such as (GC) with a sulfur specific detector (AED) would be installed to analyze the feed to a hydrotreating unit. The analyzer would be calibrated to quantify the individual sulfur compounds or classes of sulfur compounds present in the feed. The output from the analyzer would be linked to the unit's distributed control system to automatically change temperatures and feed rates to change hydrotreating severity. This invention could bring economical benefits by increasing the life of the hydrotreating catalyst, reducing operating cost, and decreasing the potential amount of offspec product. In one embodiment, the hydrotreating is a hydrodesulphurization process.