DevelopmentofChinaDigitalSeismologicalObservationalSystemsduring1996~2000andtheCapitalCircleAreaSeismographNetworkduring1999~2001areintroduced,andthestationdistributions,instrumentsused,maintasksofNationalDigitalSeismographNetwork,RegionalDigitalSeismographNetworkandPortableDigitalSeismographNetworkareintroducedchiefly.