Barrier layer of nBn InSb is analyzed from energy band,Sentaurus TCAD is used to calculate and simulate IV performance of nBn InSb infrared device.The simulation results show that,the gradient layer is introduced near the absorption layer side in the barrier layer,and it can effectively improve the performance of the device.And then,the influence of Al composition and thickness of the barrier layer on the device performance are analyzed.According to the simulation results,selected structural parameters are used to grow nBn InSb by MBE,and the testing results of the device are given.