Abstract: Objective This study aims to obtain welding heat input parameters of S32304+Q390C clad pipes that meet service requirements. Methods Welding tests were carried out on S32304+Q390C clad plates with three arc welding processes, plasma arc welding, submerged arc welding, and gas tungsten arc welding. After welding, microstructure and Vickers hardness of base layer, transition layer, cladding layer welds and their corresponding heat-affected zones under different welding heat inputs were analyzed. Meanwhile, tensile properties and corrosion resistance of welded joints were evaluated. Results The test results show that microstructure of base layer weld consists of pearlite and ferrite, and weld grains are gradually refined with increasing welding layers. When welding heat input of transition layer weld increases from 1.68 kJ/mm to 1.92 kJ/mm, its microstructure transforms from austenite plus skeletal ferrite to austenite plus lath ferrite. As heat input rises from 1.96 kJ/mm to 2.24 kJ/mm, dendritic characteristic of skeletal ferrite becomes prominent and a local network structure forms. When welding heat input of cladding layer weld decreases from 2.64 kJ/mm to 2.11 kJ/mm, austenite phase fraction increases from 40% to 45%. Welded joint with transition layer/cladding layer interface above clad plate interface achieves a tensile strength of 668 MPa and a corrosion potential of −189 mV, while the joint with interface below clad plate interface exhibits a tensile strength of 648 MPa and a corrosion potential of −215 mV. Microhardness of transition layer weld increases with rising welding heat input, reaching a maximum value of 389 HV0.1. Conclusion The optimal gas tungsten arc welding process for S32304+Q390C clad pipes is as follows, welding heat input of cladding layer weld should be controlled below 2.00 kJ/mm, and welding heat input of transition layer weld should not exceed 1.50 kJ/mm. Multi-layer and multi-pass welding is adopted, ensuring that transition layer/cladding layer weld interface is higher than clad material interface.