The invention discloses a method for protecting computer network security. The method includes the following steps that: a server assigns a credit value to a user and determines access authorization authority according to the credit value; the server detects an access authorization request sent by the user; the server converts the authorization request into a plurality of access authorization sub-query tasks and authenticates the plurality of access authorization sub-query tasks respectively; when detecting an access request of the user, the server authenticates the user at first; after receiving an access approval feedback, the user sends a data search instruction to the server and carries out corresponding operation on the server; searched data are downloaded to the terminal computer of the user; and the terminal computer encrypts the downloaded data and then stores the downloaded data in a disk. The method for protecting computer network security of the invention has high universality and is applicable to situations having high data security requirements. The server is provided with a security encryption chip, so that information leakage caused by a condition that the server is externally connected with the Internet can be effectively prevented, and the security of hardware information can be ensured.