CaO containing carbon pellet (CCCP) for calcium carbide production was proposed in this work. The occurrence of impurities in both pulverized char and carbide slag is normally inevitable. This study is to examine the effects of the inorganic oxides on the microstructure and thermal strength of CCCP. Three different CCCPs of Ca(OH)(2) + raw char (CRC), carbide slag + raw char (CSRC) and Ca(OH)(2) + demineralized char with various impurities were prepared for the purpose of comparison. The results showed that the order of thermal strength of three kinds of CCCPs was as follows: Ca(OH)(2) + raw char (CRC) > carbide slag + raw char (CSRC) > Ca(OH)(2) + demineralized char (CDC). Four kinds of oxides (i.e. SiO2, Al2O3, Fe2O3 and MgO) as impurities could all possibly react with CaO to form low-melting eutectic matters to different extents, thus resulting in the decrease in the stability of CaO pellet. The presence of CaF2 in the demineralized char has caused over-sintered CaO grains and reduced the thermal strength of CDC. Meantime, the isothermal and non-isothermal experiments have revealed that the CaO grain sintering process could be well expressed by the model of "porous body sintering". (C) 2018 Elsevier B.V. All rights reserved.