A new liquid flow based on differential pressure sensor , described its basic principles and methods to complete the calibration experiment at a certain temperature for a specific size of the sensor. Experimental results show that the sensor can be manufactured by the liquid flow, velocity actual detection range from 5 to 170ml / s. By changing the pressure sensor model , amplifier gain and catheter size , it is easy to improve the sensitivity of the sensor and the extended range . Further, the principles and the design of the proposed sensor also has the following advantages : in such a sensor tube no moving parts and choke member ; the use of differential pressure principle catheter design.