A travel time difference method ultrasonic flowmeter based on field programmable gate array（FPGA） is designed.The hardware structure and realization method are introduced.The software function and work mode are overviewed.The hardware structure of the system is microcontroller+FPGA.The microcontroller is the control center.Making use of the programmable characteristic

the rich inner resources and very high work frequency of a FPGA chip

a date signal processes module including a high speed counter is designed.The reliability and the measurement precision of system are improved.And the hardware can be upgraded more easily.