Abstract: Digital certificate is an electronic certificate issued by the CA. The technology uses public key and private key for data encryption mode，it can effectively guarantee the security of data during transmission， therefore， the digital certificates have been widely applied to authorized identity management，trusted website services，terminal security protection，e-mail security and code signing protection，so as to effectively guarantee the security of the network. The author introduced the digital certificate briefly，then analysed the principle of digital certificate，at last，pointed out the application of digital certificate in network security.

Key words: digital certificates, network security, encryption, digital signing