Abstract: Thermogravimetric behavior and products distribution of the co-coking of coal from Shougang coking plant with waste plastics from municipal solid waste of Beijing were studied using thermal balance and 10 g fixed-bed reactor. The results showed that the temperature range of weight loss of Shougang blend coal was from 300 ℃ to 750 ℃, but for waste plastics it was from 300 ℃ to 550 ℃. Co-coking of blend coal and waste plastics made tar yield increase and water yield decrease in the overlapped decomposition temperature region for the synergism between them. Moreover, the new idea and formulas of synergism extent were proposed as and . Based on the formation, the conclusion was obtained that the maximum synergism occurred when the ratio of waste plastic added was 1%.