Recently, about 70 Small Modular Reactors (SMRs) are being developed around the world due to various advantages such as modularization, flexibility, and miniaturization. An innovative SMR (i- SMR) is being developed in South Korea as well, and the domestic nuclear utility is planning to apply for the Standard Design Approval in 2026 after completing the basic design and standard design. Accordingly, the regulatory body is conducting research on the regulatory system for reviewing the i- SMR standard designs by referring to the IAEA and the U.S. NRC cases. A SMR is expected to many changes not only in terms of cyber security due to new digital technology, remote monitoring, and automatic operation, but also in terms of physical security according to security systems, security areas, and vital equipment. Accordingly, related technical documents issued by the IAEA require nuclear utilities to consider regulatory requirements of security from the design phase by integrating security regulations into SMR licensing. The U.S. NRC has also identified 17 issues affecting SMR design since 2010 (SECY-10-0034), and among them, ‘Consideration of SMR security requirements’ was included as a major issue. Accordingly, the NuScale applicant conducted security assessment and design in consideration of the Design Base Threat (DBT) in the initial SMR design process through the Gap Analysis Report (2012) and the NuScale’s Security System Technical Report (TR-0416-48929), and the NRC developed the Design Specific Review Standard for NuScale (DSRS) and then reviewed the applicant’s security design process, standard design results, and testing criteria for security system (ITAAC). This paper analyzed the case of security review activities during the NuScale standard design review, and through this, it is intended to be used in the development of domestic regulatory system for the i-SMR security review in the future.