In order to solve the identity authentication problem of network applications, the OAuth2.0 protocol has been widely used in the actual production environment. However, many systems use the OAuth2.0 standard unreasonably in their design, which results in many security flaws. This study analyzes the security problems of OAuth2.0 protocol in recent years, including the man-in-the-middle attack, authorization hijacking vulnerability, and CSRF vulnerability, and the study proposes a password-based Schnorr digital signature and OAuth2.0 strong identity authentication scheme for solving these security problems. Finally, the security of the scheme is analyzed. The results show that the scheme has excellent security and is easy to use.