The invention provides a method and apparatus for protecting a cache resource of a network printer, which is applied to an access switch. The method comprises the following steps: receiving a message transmitted to a network printer; detecting the message by virtue of a pre-configured illegal message detection rule; and when the message is an illegal message, abandoning the message. In the method of the invention, the detection rule of the illegal message is pre-configured in the access switch, and the access switch can detect the message transmitted by a user to the network printer by virtue of the detection rule and can determine whether the message is the illegal message or not. If the message is the illegal message, the access switch can abandon the message, so that the cache resource of the network printer can be protected.