Pyrolysis to recover oil accompanied by semi-coke combustion can realize the high-efficiency and staged utilization of low-rank coal,which is the research hotspot of high-efficiency utilization of low rank coal. However,because of its low volatile,the ignition temperature of semi-coke is high,and it is hard to burn out as well. The addition of flux is a promising method to improve the combustion properties of the hard-to-burn semi-coke with low volatile. In this paper,the effects of alkali（K2CO3)and alkaline metal（CaCO3)on the combustion characteristics of semi-coke were studied by thermogravimetric analysis,and the activation energy of the semi-coke combustion were investigated by Kissinger-Akahira-Sunose（KAS)model. The results show that the semi-coke has the high ignition temperature and low combustion reactivity. The inherent mineral matters in semi-coke have some catalytic effects on its combustion performance. The addition of CaCO3 has little promotion effect on the characteristics of semi-coke combustion,which indicates that CaCO3 does not improve its combustion properties. However,compared with alkali earth metal CaCO3,the addition of K2CO3 obviously lowers the ignition temperature,the peak temperature of combustion and the combustion index. At the same time,with the increase of addition ratio of K2CO3,the apparent activation energy of semi-coke combustion decreases obviously,which means that the addition of K2CO3 can apparently improve the combustion reactivity of semi-coke. 2% addition of K2CO3 shows the best improvement for the combustion of semi-coke in this experiment,and the dispersion effect of adding K2CO3 by impregnation method is better. In addition,the addition of K2CO3 with impregnation is more favorable for the improvement of semi-coke combustion than physical mixture.