A gradient nano-submicro-structure was obtained in metal surface via surface deformation nano-crystalline technology, which can provide severe plastic deformation on metal surface by external force. This unique gradient structure can not only be used to promote nitriding process of metallic materials, but also significantly be beneficial to form excellent nitriding layer, which can improve the comprehensive properties and service life. Therefore, it showed good application prospect in many fields. Recently, more and more investigations were focused on improving nitriding via surface deformation nano-crystalline pre-treatment, due to the academic and industrial application value. In the present article, the effect of surface deformation nano-crystalline on nitriding behavior is summarized in detail. Finally, the problems existed on the enhancement of nitriding are pointed out and it is also predicted what should be made in the future.