An online detection method based on differential pressure technology was proposed to test the grinding wheel wear,aiming at the question how to real time online detect the grinding wheel wear.An online noncontact detection system was established.The experimental results show that: the method can be used to realize online noncontact detection of grinding wheel wear,measuring range can be up to 120 μm,and linearity is 18%,repeatability of the measurement system is less than 1%.The characteristics of the measuring system are simple and locale application.