Abstract: Utilizing instrumented impact test,different determination methods for dynamic ductile fracture toughness JId using single specimen were compared.The applied scopes of different single specimen methods were discussed based on the results from low blow tests.It is indicated that energy method before maximum loading is reasonable to the high strength steels which have little deformation strengthening after crack initiation,compliance changing rate method should not be used to evaluate the dynamic ductile fracture toughness of materials with high tearing resistance,and JId values could be obtained conveniently by determining critical stretch zone width for the material with a crack tip blunted along half circle.