Abstract: Low quality coal can be fired in a circulating fluidized bed (CFB). The multiple parallel cyclones are wide- ly used to separate the gas-solid flow in CFB boiler,however,the performance in parallel cyclones are different,indica- ting the non-uniform gas-solid flow into parallel cyclones. This paper experimentally investigates the performance of three parallel cyclones in CFB boiler. It is found the middle cyclone has greater pressure drop,and higher collection ef- ficiency,which indicates higher flue gas flux into the middle cyclone. The performance of parallel loop-seals and stand- pipes are different as well. The middle loop-seals and middle standpipe have lower pressure drop,indicating lower sol- ids flux into the middle cyclone. The lower solids flow into the furnace at the middle position is not beneficial to the even solids distribution in the furnace,leading to the decrease of SOx remove efficiency. In addition,the uneven distri- bution of gas-solid flow would make the greater temperature increase of flue gas through the middle cyclone.