Local resistances caused by abrupt expansion and contraction were experimentally investigated for the small channels with diameters from 0.330 mm to 0.580 mm by using a novel pressure measurement method of the tiny gaps on the channels.The experimental results showed that the pressure measurement method through the gaps was a feasible method for small channels.For laminar flow，the expansion loss coefficient was much lower and the contraction loss coefficient was much higher as compared with the experimental results of conventional channels，while for turbulent flow，the expansion and contraction loss coefficients were consistent with those of the conventional channels.