The distributing gas performance of the pipe distributor was analyzed based on the flow field numerical simulation of pipe distributor used in FCCU （Fluid Catalytic Cracking Unit).The result from simulation shows that the pressure increases along the branch pipe and the axial flow rate decreases，which leads to the nozzle flow rate increasing gradually.Furthermore，an obvious bias flow was found in the inlet of branch，which brings the nozzle flow rate less than the designed flow rate and causes an uneven gas distribution in the fluidized bed.Meanwhile，the momentum equation with variable-mass flow was applied to analyze the flow in the pipe distributor.The flow type in the branch pipe belongs to the “momentum exchange controlling model”.The pressure in the branch pipe always increases from the inlet to the end and the pressure distribution is not consequentially uniform.The uneven gas distribution of the pipe distributor results in fluidized gas non-uniformity in the bed and the erosion in branch pipe and nozzle.Finally，according to the pressure characteristics in fluidized bed system，relationship between the pressure drop of branch pipe and pressure drop of nozzles，as well as of the critical nozzle pressure drop and the designed nozzle pressure drop，was discussed.The gas distributor performance could be optimized by means of the structural improvement of branch pipe.