A method for identity authentication, comprising: detecting (201, 501), by a browser kernel unit, a login trigger event, and sending the login trigger event to a Web application unit; determining (202, 502), by the Web application unit, a website address corresponding to a login trigger operation according to the login trigger event, and sending the website address to the browser kernel unit; sending (203, 503), by the browser kernel unit, an access request to an application server according to the website address sent by the Web application unit; and receiving, by the browser kernel unit, identity authentication-needed indication information returned by the application server according to the access request, wherein the identity authentication-needed indication information carries an identity authentication defining parameter, and determining a selected user digital certificate which tally with the identity authentication constrain parameter through performing a screening to user digital certificates according to the identity authentication defining parameter, wherein the identity authentication constrain parameter includes any one or more of a certificate issue, a certificate type, a signature algorithm and a public key algorithm; generating (101, 205, 507), by the browser kernel unit, a login request carrying the selected user digital certificate according to the selected user digital certificate, and sending the login request to the application server; receiving (102, 206, 508), by the browser kernel unit, a response indicating authentication success which is returned by the application server after performing identity authentication according to the selected digital certificate, extracting a webpage file from the response, parsing the webpage file, generating a webpage and sending the webpage to a browser interface unit; and displaying (103, 207, 509), by the browser interface unit, the webpage. detecting (201, 501), by a browser kernel unit, a login trigger event, and sending the login trigger event to a Web application unit; determining (202, 502), by the Web application unit, a website address corresponding to a login trigger operation according to the login trigger event, and sending the website address to the browser kernel unit; sending (203, 503), by the browser kernel unit, an access request to an application server according to the website address sent by the Web application unit; and receiving, by the browser kernel unit, identity authentication-needed indication information returned by the application server according to the access request, wherein the identity authentication-needed indication information carries an identity authentication defining parameter, and determining a selected user digital certificate which tally with the identity authentication constrain parameter through performing a screening to user digital certificates according to the identity authentication defining parameter, wherein the identity authentication constrain parameter includes any one or more of a certificate issue, a certificate type, a signature algorithm and a public key algorithm; generating (101, 205, 507), by the browser kernel unit, a login request carrying the selected user digital certificate according to the selected user digital certificate, and sending the login request to the application server; receiving (102, 206, 508), by the browser kernel unit, a response indicating authentication success which is returned by the application server after performing identity authentication according to the selected digital certificate, extracting a webpage file from the response, parsing the webpage file, generating a webpage and sending the webpage to a browser interface unit; and displaying (103, 207, 509), by the browser interface unit, the webpage.