Abstract: Hydrogen embrittlement behaviors of tubular steel API-P110 in the acid solution dissolved 50% H₂S and 50% CO₂ or 50% H₂S only were investigated by immersion test, sulfide stress cracking corrosion (SSC) at the constant loading, and electrochemical hydrogen permeation test. Effects of CO₂ on hydrogen embrittlement corrosion behavior are discussed. Compared to that of steels without being corroded, in H₂S and CO₂ or H₂S only, the tensile strength(σ_b), yield strength (σ_s) and elongation rate at rupture(δ_c) of steel decline; comparing with in H₂S only, the strength and elongation of steel in H₂S and CO₂ decline less, embrittlement rate is low, the SSC susceptibility of steel lightens, and hydrogen permeation rate(J) decreases. In various corrosive environment, hydrogen permeation density (JH) dramatically increases to peak value as time goes on, then descend slowly until the steady state appears. In high H₂S, CO₂ improves compactness of corrosion scale, and decreases the content of Fe_xS_y in scale. Therefore, the amount of hydrogen permeation in H₂S and CO₂ is more than in H₂S only, as results in the susceptibility of hydrogen embrittlement of steel decreases.