Abstract: Nondestructive test(NDT) technology is the important technical support for laser additive manufacturing alloy steel components, the key technology to ensure laser additive manufacturing production quality and in-service safety and the important technical composition to the production safety guarantee through life cycle. The formation, texture and mechanics properties of alloy steel components made by laser additive manufacturing are different from those made by traditional technologies, so NDT technology faces many challenges. The forming quality characteristics of laser additive manufacturing alloy steel were summarized, including forming flaws and mechanics properties; Based on the development of NDT technologies, the applications of NDT technologies in laser additive manufacturing were reviewed, especially in applications of material mechanics properties and flaws; Based on ultrasonic and micro-magnetic techniques, micro-magnetic sensor design scheme, calibration method and principles of evaluating the material mechanics properties were outlined; Finally, the challenges and prospects of NDT in laser additive manufacturing alloy steel components were discussed.