A maintenance method for network connection and a computer system are provided. The method is adapted to a computer system having a timer. The timer is configured to regularly wake up the computer system to check whether a network connection is working normally. In the method, the computer system is waked up at intervals of a first time interval within a predetermined period and a current IP address of the computer system is extracted. The predetermined period is divided into a plurality of periods by the first time interval. Whether a change occurs on the IP address is determined within each of the periods, and accordingly the computer system is waked up to check the network connection.