Abstract: It is critical for the enhancement of coal conversion to understand the non-catalytic synergistic effect of coal and biomass copyrolysis. In this paper,four indicators for determining the occurrence and intensity of synergistic effects during coal-biomass copyrolysis process,namely the temperature range,the thermo-gravimetric curve,the apparent activation energy,and the yield of pyrolysis products and their composition,are summarized based on the researches in recent years. Then the effect of the influence factors,including internal and external factors,on the non-catalytic synergy of co-pyrolysis is also discussed. Moreover,the research progress and achievements on the reaction mechanism of the non-catalytic synergistic effect reported in recent years are also reviewed briefly. Based on these discussions,some possible challenges are proposed for future research.