The invention discloses a field bus interface for a bus type detection element of a numerical control machine, which is used for communication between a position detection element on the numerical control machine and an external control module of the numerical control machine. The interface comprises a field programmable gate array (FPGA), an Ethernet physical layer (PHY) chip, a network transformer and a twisted pair joint, wherein the field programmable gate array (FPGA) is used for the transmission buffer and reception buffer of data, and protocol processing; the Ethernet physical layer (PHY) chip communicates with the field programmable gate array (FPGA), and is used for transmitting and receiving the data and converting differential analogue signals transmitted in a network into digital signals for the processing of the field programmable gate array (FPGA); the network transformer is connected with the Ethernet physical layer (PHY) chip, and is used for isolating the signals; andthe twisted pair joint is connected with the network transformer, and is used for transmitting and receiving the analogue signals. The field bus interface can increase the communication rate of a busto 100M and reduce transmission delay to be within one microsecond, and meets the requirements of high-speed and high-accuracy machining of the conventional numerical control machine.