Ultrasonic anemometer (UA) is a core application in natural environment measurement. As well known, mechanical anemometer works well in good weather but it is not suitable to be applied in bad environment such as polar region and upper air. On the other hand, ultrasonic anemometer works well in most situations. Moreover, ultrasonic anemometer has wider detectable wind speed range. It can be said that ultrasonic anemometer is a more advanced instrument to measure wind velocity. In this paper, the theory of ultrasonic anemometer is first discussed. Using the theory, a test bed is then designed and constructed to measure one-dimensional wind speed. Active Butterworth filter is introduced into the circuit in order to increase the stability and accuracy. Furthermore, we test the one-dimensional ultrasonic anemometer and compare the measured wind speed with theoretical wind speed measured by a thermal anemometer device. Error is also discussed and improvement has also made during the experiment.