The work aims to study the effect of pH value on corrosion behavior of Q235B steel in desulfurizing liquid, in order to lay the foundation for optimizing the subsequent process parameters and designing the protection coating. Immersion test and electrochemical measurement were conducted to study the corrosion behavior of Q235B steel in desulfurizing liquid with different pH values.The morphologies and element composition of corrosion products in different pH values were analyzed by SEM and EDS. When the corrosion rate of Q235B steel was measured by weight loss method, the corrosion rate decreased with the increase of pH value and change range became smaller. In the electrochemical test, the open circuit potential of Q235B steel in desulfurization solution positively shifted with the increase of pH value. There was no passivation area in the polarization curve. Self-corrosion potential positively shifted with the increase of pH value, whereas corrosion current density was on the contrary. The Nyquist graph was a nonstandard semicircular captance arc which increased with the increase of pH value. Through observation by scanning electron microscope, when pH was 4.0, corrosion products were scattered on the surface of steel and the structural shape looked like bud with void. With the increase of pH value, the corrosion products obviously increased and the structure also changed. When pH was 10.0, the steel surface was covered by a layer of rufous products, whose structure was spherical and compacted. The EDS analysis showed that corrosion products were mainly composed of Fe and O. With the increase of pH value, the proportion increased. What’s more, there was a small amount of Na, S and Zn elements. In the range of studied pH values, corrosion rate of Q235B steel in desulfurizing liquid decreases with the increase of pH value, and the corrosion is inhibited to different degrees. The increase of pH value can promote the formation of effective and compact corrosion products layers. When the pH value is lower, the corrosion of Q235B steel is mainly controlled by anode activation. With the increase of pH value, concentration of OH- increases, corrosion is controlled by cathodic oxygen depolarization, corrosion resistance is enhanced and corrosion rate declines.