The present invention provides a method for guaranteeing GGSN capability at a condition that the load of network operation capacity is high. The method comprises the following steps: measuring a safety operation capacity of GGSN device, the safety operation capacity is a maximum capacity limit which can be obtained by the GGSN device; setting a safety threshold as a base line of the GGSN device based on the safety operation capacity; restricting the capacity of an IP address pool in the safety threshold to guarantee that the number of PDP text subscriber in the GGSN device is in the base line of safety operation; and executing full-service testing after the configuration operation to guarantee the rightness of data modification. The method according to the invention actively restricts the capacity of GGSN access through adjusting the magnitude of capacity of IP address pool at the condition that the load of network operation capacity is high. The method according to the invention guarantees that the device can work normally at the condition of high load and guarantees the service quality of access subscriber.