Abstract: The desulfurization and denitrification systems face sever challenges due to the ultra-low emission rules of coal-fired boilers.CaO-based sorbents can effectively remove SO_2 from flue gas of circulating fluidized bed boilers. Char can be used as a reducing agent to reduce NO directly,and CaO plays a catalytic role in the reduction reaction of NO by char. which can realize the simultaneous SO_2 and NO removal in flue gas. Based on calcium looping technology for CO_2 capture,the simultaneous SO_2/NO removal performance of CaO/bio-char was investigated under fluidization at constant heating rate in this study to explain the effect of continuous temperature change on the simultaneous SO_2 and NO removal by CaO/bio-char. The influences of O_2 and CO_2 in flue gas on the simultaneous SO_2/NO removal performance of CaO/coconut shell char were discussed. The results indicate that O_2 can reduce the temperature of heterogeneous reduction of NO by activating carbon atoms on the surface of coconut shell char. The NO removal efficiency increases gradually with constant rate heating from 300 ℃ to 950 ℃,reaching 100% at above 780 ℃ . The SO_2 removal efficiency of CaO/coconut shell char is also promoted by O_2. The simultaneous SO_2/NO removal is inhibited by the carbonation reaction between CaO and CO_2 as well as CO_2 gasification of coconut shell char. In the presence of both O_2 and CO_2,the NO removal efficiency increases as temperature increases from 500 ℃ to 800 ℃,while the SO_2 removal efficiency firstly decreases and then increases. SO_2 inhibits the NO removal of CaO/coconut shell char,while NO can promote the SO_2 removal performance. The simultaneous SO_2 and NO removal efficiencies of CaO/coconut shell char at 800 ℃ are 97.7% and94%,respectively.