Abstract: Hardness is one of the commonly used indicators for evaluating the mechanical properties of metal materials, which intuitively reflects the differences in performance of metal materials under different welding conditions, organizational structures, and heat treatment process conditions. It can provide an effective basis for evaluating the safety level of pressure pipelines under inspection. This article analyzes the factors that cause hardness anomalies from the aspects of material performance, welding, heat treatment, etc., and proposes preventive measures and treatment plans, which can provide effective reference for obtaining appropriate hardness results after welding of high-grade material pipelines.