The invention discloses a dynamic port isolation method and apparatus for an IP monitoring system. The method comprises: a switch adds an IP address of the switch and port information of access of front-end equipment to the switch into a registration message sent to a VM by the front-end equipment; after the VM receives the registration message, the IP address of the switch and the port information of access of the front-end equipment to the switch are stored; and when target front-end equipment is requested to send a multicast message, a switch where the target front-end equipment is located as well as all ports, accessed to front-end equipment, of the switch is inquired and then all ports, accessed to the front-end equipment, of the switch are added into a port isolation group. In addition, the invention also provides a dynamic port isolation apparatus for an IP monitoring system. According to the invention, a port isolation group can be configured dynamically based on services, so that problems of static configuration and large maintenance workload can be solved.