Abstract: Experimental tests were carried out on a self-developed fluidized bed reactor for oil shale semi-coke and biomass blends at different mixing ratios, bed temperatures and fuel particle sizes, so as to obtain the volume fraction and formation mechanism of various gas components emitted from the combustion. Results show that the SO2 emission has a positive non-proportional relationship with the sulfur content in raw fuel blends. The formation mechanism of NOx is very complicated, which has a linear relationship with the nitrogen content, and can be represented by the conversion rate of nitrogen. The gaseous pollutants SO2 and NOx can be absorbed by both the oil shale semi-coke and the fuel ash. Too small particle size of fuel blends may inhibit relevant reactions and therefore lead to incomplete combustion of the fuel blends.