The invention discloses a method for remotely monitoring method of computer network. It is an improvement of the RMON (Remote Network Monitoring) alarm group. The method mainly includes: Setting an alarm-extended table in the RMON alarm group; Defining a combination object in MIB (Management Information Base) that is an expression with two or more than two independent objects; A network management center sends a Set-Request packet with the expression to managed devices to initiate a RMON monitoring process; The expression is calculated and its value is compared with a threshold; When calculated value of the expression exceeds the threshold, processing steps preset by the network management center are taken. The invention supports SNMP (Simple Network Management Protocol), optimizes network performance, and saves network bandwidth and CPU resource of the network management center.