Abstract: Using single-layer electro-slag strip cladding technology and domestic welding strip and agglomerated flux,effects of welding parameters on thickness,chemical composition,forming and mechanical properties of the cladding layer were tested for welded parts of the hydrogenation reactor. Contents of main alloying elements in four different thickness weld overlays of 4. 0~4. 5 mm,4. 5~5. 0 mm,5. 0~5. 5 mm,5. 5~6. 0 mm were analyzed,and distribution characteristics and stability of alloy components in the cladding layer with distance of 0. 5 mm and above from base metal surface were analyzed. Ferrite content and distribution characteristics of cladding layers with different thickness were tested. Thickness of the cladding layer was 4. 0~5. 5 mm to meet the technical requirements of ferrite content of 3~8 FN. Within the range of suitable process parameters,the surface of the cladding layer was well formed without defects,and chemical composition,ferrite content and side bending performance all met the technical requirements.