The security model in the previous network environment has a vulnerability in which resource access control fo r trusted users is not properly achieved using the Perimeter model based on trust. The Zero Trust is an absolute principle to assume that the users and devices accessing internal data have nothing to trust. Applying the Zero Tr ust principle is very successful in reducing the attack surface of an organization, and by using the Zero Trust, it i s possible to minimize damage when an attack occurs by limiting the intrusion to one small area through segment ation. ZTNA is a major technology that enables organizations to implement Zero Trust security, and similar to Sof tware Defined Boundary (SDP), ZTNA hides most of its infrastructure and services, establishing one-to-one encry pted connections between devices and the resources they need. In this study, we review the functions and require ments that become the principles of the ZTNA architecture, and also study the security requirements and additiona l considerations according to the construction and operation of the ZTNA solution.