The exploitation of high acid wells is facing severe corrosion challenges in the A and B gas fields in Sichuan, thus using lined steel pipe is a reliable and cost-effective anti-corrosion measure. However, lined steel pipe welding involves dissimilar steel welding, and anti-corrosion performances will be affected if the welding process is unreasonable. So it is necessary to make evaluation for corrosion of lined steel pipe. In this paper, taking welding gap of L245/825 lined steel pipe as example, the anti-SSC performances of L245/825 straight and ring welding gaps in NACE A solution were studied by CR method, and anti-cracking performances of them were evaluated by laboratory experiments. Then corrosion performances of L245/825 lined steel pipe welding gaps and L360NCS carbon steel were studied in the corrosive environment found in the Tian Dong 5-1 high sour gas well. Laboratory and field tests show that straight and ring welding gaps of L245/825 lined steel pipe have good anti-environment and anti-cracking performances of electrochemical corrosion in the high acid environment. The technology of welding process selected in the paper is reliable. Research results provide references for welding operation of L245/825 lined steel pipe in high sour gas fields.