Under pipeline coating disbondment is susceptible to microbiologically influenced corrosion, due to lack of cathodic protection (CP), humidity and low concentration of oxygen. In this study, effect of (CP) under disbonded coating in absence and presence of sulphate-reducing bacteria (SRB) has been investigated. In this regard, a simulated set up was made. Coupons were put in this set up and CP of -1200, -870 and -750 mV SCE in two conditions of presence and absence of SRB were applied in a period of 20 day- corrosion test. Local potential and pH under disbonded coating measured at different distances from Open Mouth (OM) in various times. Results showed, at the beginning of disbondment, CP dropped and then be stable at far from OM. Corrosion rate of pipeline steel under disbonded coating calculated in both conditions of presence and absence of SRB where various distances from OM and various CP applied. Weight loss measurement showed in presence of SRB, CP can control corrosion rate of pipeline steel under disbonded coating. CP efficiency decreased in presence of SRB. In all conditions of CP and in both environments of presence and absence of SRB, pH at the bottom of disbondment moved towards acidic values. But these values in presence of SRB were positive than in absence of SRB. Local pH increased with increasing the CP. In all conditions of CP, more pits were occurred at the bottom of disbondment in presence of SRB, but in absence of SRB, more pits were occurred at the middle of disbondment area