Welding process of boss of hydrogenation reactor

The invention relates to a welding process of a boss of a hydrogenation reactor. A port in one end of a cylindrical shell section is processed flatly after coiling, circle checking and flaw detection of the cylindrical shell section are qualified; and then a surfacing position of the boss is marked, and thus the trouble that a cylinder body is firstly leveled and then overturned for surfacing the boss when the boss is surfaced is avoided, the leveling procedure during processing of the boss is avoided, therefore the production time is saved, the levelness of the boss is ensured, and the purpose of ensuring the welding quality of the boss is achieved.