Abstract: Based on the principle of reflective fiberoptic sensor, a method of online noncontact testing for roller abradability is proposed. The measurement of the reflective light intensity is utilized in the method. Also a practical circuit for reflective fiber displacement sensor in testing roller abradability is introduced emphatically. According to the characteristic and the accuracy requirement of the testing course for the roller abradability, the principle, the construction and the function of the sensor circuit are elaborated and analyzed. The theories and experiments show that the proposed circuit system is stable, both the accuracy and the sensitivity can meet the demand of the actual application. And the circuit also suits for other testing systems, in which the reflective fiber displacement transducers are used under the similar condition after a slight modification.