Abstract: Taking K8206 working face of Yangquan No.3 coal mine as engineering background.The influence laws of working face width on the developmental morphology of mining fissure"O-shaped"circles are studied by using discrete element numerical simulation software UDEC and laboratory similar simulation experiment.The simulation results show that the changes of working face width have significant impact on mining fissure"O-shaped"circle,and the width of mining fissure"O-shaped"circle will increase with the increasing of working face width under certain key stratum structual conditions.The working face width has little effect on the height of mining fissure"O-shaped "circle,and the height of mining fissure"O-shaped "circle is ended at the main key stratum of overlying strata when working face length changes within a certain range.