The anticorrosion performance of carbon steel in 55% LiBr solution containing PMA/SbBr3 inhibitor was studied by weight-loss tests, electrochemical measurements and surface analysis. In 55%LiBr+PMA/SbBr3 solution, corrosion rates of carbon steel at 145 ℃, 175 ℃, 190 ℃ and 240 ℃ are 18.32 μm·a-1, 27.68 μm·a-1, 53.58 μm·a-1 and 73.78 μm·a-1, respectively. PMA/SbBr3 inhibitor may inhibit the corrosion of carbon steel in 55% LiBr solution effectively. Especially, it shows an excellent corrosion inhibition performance at high temperature. Both anodic and cathodic reactions of carbon steel may be inhibited by PMA/SbBr3 inhibitor, so it may be classified as mixed inhibitor. In 55%LiBr+PMA/SbBr3 solution, the apparent activation energy of the corrosion reaction of carbon steel is 29.61 kJ·mol-1. The corrosion inhibition mechanism of PMA/SbBr3 is suggested as follows: PMA has the effect of inhibiting hydrogen evolution and a strong oxidizing property; Sb3+ also exhibits oxidizing properties, and can exist stably with PMA in LiBr solutions; the passive film comprising Fe2O3 and antimony formed on carbon steel surface may prevent Br- from diffusing into the metal surface due to the synergistic effect of PMA and Sb3+; As a result, the anticorrosion performance of carbon steel may be improved by PMA/SbBr3 inhibitor in 55% LiBr solution.