The present invention discloses a device and a method for protection of a thyristor set string. The device comprises a man-machine interaction module, a main controller, a triggering module, a dynamicmonitoring circuit and a thyristor set string. The man-machine interaction module is connected with the main controller, and the triggering module is connected with the thyristor set string; and thedynamic monitoring circuit is connected with the triggering module and the main controller, and the dynamic monitoring circuit comprises a field-programmable gate array logic gate constructor, a microsecond time divider, a comparator, an imbalance degree determiner, a first optical fiber input device and a first optical fiber output device. The device and the method are provided with the dynamic monitoring circuit to achieve monitoring and protection of thyristors to achieve safety early warning of the thyristors so as to discover transformation of early-stage performance parameters of the thyristors.