The modification greatly improved konjac glucomannan (KGM) characteristics and expanded its application range. For this purpose, the combination of acidolysis with oxidation was chosen to modify KGM in a heterogeneous system. In this study, we mainly discussed the effect of acidolysis and oxidation on the structure and properties of KGM. The experimental results indicated that the acidolysis and oxidation destroyed the structure of KGM particles, and reduced its crystalline degree. The size of derivatives was greater than that of KGM, and their surface became very rough. The acidolysis and oxidation decreased obviously the swelling capacity of KGM, but increased the acid and alkali resistance. The thermal characteristic parameters of KGM such as onset decomposition temperature, onset temperature, peak temperature, enthalpy change, and so on were affected by the acidolysis and oxidation. The oxidation of hydrogen peroxide did not led to any carboxyl groups being introduced into KGM molecular chains, whereas it resulted in the reduction in the viscosity of KGM. There is no synergistic effect between KGM or its derivatives and starch paste.