Abstract: This paper deals with design and operation of an automated fatigue test system with closed-cycle control. It compares favourably with previous systems with open-cycle load control in amplitude precision. The major advantage of its advanced core device YZP-2 is a highly uniform bending load provided by eliminating the perturbing effect of excitation. This electronically servo-controlled system with eddy-current transduser gives automatically the blade fatigue failure signal by monitoring frequency transition of the test specimen so as to provide precise test data for S-N curves. This new system works satisfactorily over 1000 hours in our laboratory.