Abstract: In order to reveal the effect of the tetra-component complex compound biocide on the bactericidal and corrosion-inhibiting behaviors and rule of sulphate-reducing bacteria (SRB) biofilm on N80 steel surface with different surface finish levels, the effects of compounded biocide on the action mechanism and bactericidal corrosion inhibition of N80 steel with different finishes under the environment of SRB were investigated by using weightlessness measurement, surface analysis and electrochemical analysis. The results show that the corrosion rate of N80 steel in SRB environment without biocides decreases with the increase of surface finish, this is due to the lower the surface finish of N80 steel, the greater the effective area of SRB attachment, and the metal surface electrons are more likely to react with environmental media, the more serious the corrosion. In the SRB environment with the addition of compound biocide, the corrosion inhibition rate ranges from 45.0% to 57.7%, which indicates that the effect of compound biocides on slowing down the corrosion of N80 steel is significant. This is due to the fact that tetrakis hydroxymethyl phosphonium sulphate(THPS) in the compound biocides contains hydroxymethyl groups that damage bacterial cell membranes and proteins. Cecropin can affect the synthesis of bacterial cell wall, ultimately inhibit the bacterial proliferation; the D-tyrosine-enhanced biocides act as a signal molecule to inhibit the production of extracellular proteins, prompt biofilm decomposition and shedding, destroy the oxygen-concentrated environment and slow down the corrosion of N80 steel.