Abstract: For the requirements of high precision and low power in Ultrasonic Flow-meter, an self-adaptive sampling method is proposed in order to overcome the deficiency of periodic sampling.The sampling rate of change in the adjacent time difference is considered as the parameter to control sampling period, which can be adjusted automatically based on the fluid flow.Through the comparative analysis of experimental data between self-adaptive sampling and periodic sampling, adaptive sampling method can not only significantly improve the measurement accuracy in a fluid fluctuation environment, but also can reduce system power consumption while the fluid is stable.