Abstract: This study tells the story of in order to effectively resist the invasion of external .NET platform system, improve system security, it must establish the prevention and monitoring technologies improve system security system. System programmer and administrators only in the system design stage, to do a safety prevention programs and solutions to security applications; finally put forward the platform system safety prevention programme. in addition, this study analyzes the study of the .NET application process, three elements of security (authentication, authorization, fake) their own characteristics; Secondly, in detail .NET environment based on common security vulnerabilities and security architecture .NET environment; Finally, the study of the IIS and .NET authentication mode application and authorization mechanisms and their intranet and internet environment to achieve the security policy configuration and design.