Cyclone separator is one of the important equipment in circulating fluidized bed boiler,which has the advantages of simple structure and low cost. However,many accidents such as deformation,crack,downward movement and even falling off of the vortex finder of the cyclone separator are easy to occur during the operation of the circulating fluidized bed boiler,resulting in serious economic losses.A cyclone separator without vortex finder was presented,and the dust free fresh air was introduced into the original vortex finder to form an air curtain to adjust the separation efficiency of cyclone separator,which could avoid the failure accident of vortex finder and flexibly adjust the separation efficiency of cyclone separator. The separation performance of the cyclone separator was studied by cold state experiment and numerical simulation. The results show that the separation efficiency of the cyclone separator decreases after the vortex finder falls off. Then the separation efficiency of the wind behind 3,6,9 and 12 m/s respectively increases first and then decreases. When the air curtain velocity is 9 m/s,the separation efficiency is the highest,which is 3.17% higher than that of the cyclone separator without air curtain. After the shedding of the vortex finder,the fractional separation efficiency of particles with particle size less than 6 μm shows little change compared with that in the presence of the vortex finder. However,the fractional separation efficiency of particles with particle size greater than 6 μm is significantly lower than that in the presence of the vortex finder. The separation efficiency of cyclone separator for particles with particle size less than 6 μm can be greatly improved behind the wind. After the vortex finder of cyclone separator falls off,the pressure drop will decrease slightly. When the fresh air is introduced into the original vortex finder,the pressure drop behind the wind will increase,and the pressure drop will increase with the increase of the wind curtain speed.