USB bus or fast ethernet can no more meet the distance or speed requirements for the high speed transmission with huge amount of data of a certain IR array detecting system.So the gigabit ethernet transmission system is designed and has been applied to the IR array detecting system successfully.After analyzing the implementation technology of gigabit ethernet deeply and considering the special need of the IR array detecting system,this design uses the simplified and optimized method to implement full-duplex MAC logically in the FPGA,and realizes the duplex,high speed and real-time transmission of the IR array detecter′s image and control command packages of PC.And it displays good performance in practical application.