In allusion to the deficiency of image detecting ability of current network security system, anintelligent network security system model is developed based on image content detecting. It adopts aninformation-feedback and knowledge-aid mechanism, brings forward an image content retrieval algorithm based on layout feature extraction and multi-agent technology as the kernel of image content detecting-analysis model, and realizes a security-auditing mechanism based on genetic algorithm to audit and mine the history knowledge base intelligently.Therefore,it can improve the security and reliability of yhe network system.Furthermore,a prototype of the system model is described.