Abstract: Objectives Failure mechanism and protective performance different of 10 mm thick high-strength ship steel was investigated subjected to penetration-deflagration of reactive fragment and penetration of inert fragment. Methods A 12.7mm caliber ballistic gun was used to shoot cylindrical fragment on high-strength ship steel by experiment method. Reactive composite fragment and inert steel fragment with similar density and quality were interacted with high-strength steel target, respectively. Then fragment damage mechanism, target failure mode, energy absorption and release characteristics were compared. Naval standard ballistic limits V50 of ship steel target were obtained under different fragment damage. Results Results indicate that ballistic limits V50 of ship steel target against inert and reactive fragment were 807m/s and 874m/s, respectively. Perforation ability of reactive fragment is superior to inert fragment, but expanding ability of reactive fragment is inferior to inert fragment. The impact process of reactive fragment is accompanied by strong firelight coverage and its total penetration-deflagration energy is higher than the single penetration kinetic energy of inert fragment. Conclusions Experiment results can provide data support and guidance for the design of ship protective structures and the application of active damage technology.