Abstract: In this paper,the Hulunbuir coal and three hydrogen-rich organic compounds (cellulose,polyvinyl pyrrolidone (PVP),and high-density polyethylene (HDPE)) were used as raw materials to investigate the behaviors of thermogravimetric,the changes of free radical concentration,and the changes of the yield of pyrolysis products on the fixed bed of the co-pyrolysis process and compare with the results of single pyrolysis. The interaction of free radical fragments produced by pyrolysis of different raw materials during the co-pyrolysis was analyzed. The results show that the weight loss of co-pyrolysis of coal/cellulose,coal/PVP,and coal/HDPE at 150-600 ℃ are 61.18%,60.26%,and 64.31% respectively,which are all lower than the calculated values of 62. 55%,63. 53%,and 66. 76%; When the temperature is higher than 400 ℃,the experimental value of free radical concentrations in the co-pyrolysis process are all lower than the calculated value (an average of individual pyrolysis results); According to fixed-bed pyrolysis results,the solid yields are 37. 9%,39.0%,and 34.0%,respectively,which are equal to or slightly higher than the calculated values (37.5%,36.5%,and 33.6%),the liquid (including water and tar) yields are 33.3%,44.9%,and 53.2% respectively,which are all lower than the corresponding calculated values (39.8%,51.3%,and 57.1%),and the gas yield are 28.8%,16.1%,and 12.9%,which are all higher than the calculated values (22.7%,12.2%,and 9.3%). During the co-pyrolysis process,the free radical fragments generated from different raw materials will interact with each other in the process of escaping from the bed. Among them,the combination of volatile free radicals and stable free radicals is the most important. The resistance of volatile free radicals increases,leading to an increase of the secondary reaction of the volatiles.