The invention discloses a method and system for content categorization, which aims at reducing the processing burthen of the content categorization as well as the network transmission traffic. The method comprises: transmitting, by a content categorization requester, a content digest of a content to be categorized to a content categorization provider; and performing, by the content categorization provider, content categorization according to the content digest. The device for requesting content categorization comprises: a digest operation determination component, adapted to determine whether it is necessary to obtain a content digest of a content to be categorized; a digest obtaining component, adapted to obtain the content digest of the content to be categorized when the digest operation determination component determines it necessary to obtain the content digest of the content to be categorized; and a first transmit component, adapted to transmit the content digest obtained by the digest obtaining component.