Abstract: The way of the flow measurement by the traditional Doppler ultrasonic flowmeter is detecting the statistic- average value of the flow velocity, which could not reflect the distribution of the flow velocity The greater tke Reynolds number changes, the larger the measurement error is. In order to measure zonal fluid velocity, using the Doppler ultrasonic method to controll the area of info window is presented. In this paper, for one hand, a set of ultrasonic emitter has been developed to slenderize the beam of acoustic wave, and also a set of receiver has been developed to select the back scattered acoustic wave according to the position of the scattering particle, so that, the info window has been controlled within a narrow area; A equipment which can simulate flow has been developed, so as to simulate the flow velocity of a small area of the total section. Covering the small measurement area with info-window, zonal fluid velocity is measured.