The invention relates to an AC type lightning arrester on-line monitoring device detector which is used for detection of lightning arrester on-line monitoring device. The detector employs an AC power supply and consists of a power supply part, a counter detecting part, and a milliammeter detecting part; the power supply part is supplied by commercial power AC 220V; elements include a transformer for an AV220V/AC28V AC instrument and an AV 220V/DC9V rectification power supply; in the counter detecting part, a 1000V tramegger, a double-throw switch, a capacitor, and a lightening arrester on-line monitoring device constitute a detection circuit; and in the milliammeter detecting part, a digital display milliammeter, the lightning arrester on-line monitoring device and a carbon film potentiometer constitute a detection circuit. The AC type lightning arrester on-line monitoring device detector solves a problem that no special-purpose apparatus is used to perform comprehensive performance detection on the lightning arrester on-line monitoring device and is simple in structure, easy in operation, easy to carry on a production side and high in safety.