A cold state metal plate strip surface treatment system and a treatment method thereof, used for high-pressure jet-flow descaling and rinsing metal plate strips, includes a high-pressure jet-flow descaling section. A tension unit and a stabilizing roller are provided in front of the high-pressure jet-flow descaling section, and a stabilizing roller, a compressed air drying device and a tension unit are provided after the high-pressure jet-flow descaling section; at least one descaling unit is provided in the high-pressure jet-flow descaling section, wherein the descaling unit includes first and second bending rollers used for bending a metal plate strip, and correspondingly first and second jet-flow descaling nozzles, and first and second rinsing nozzle sets. The present invention can be used for replacing the prior cold state continuous descaling pickling sets for metal plate strip, to meet the requirements of the rapidness and continuousness of modern cold-state metal plate strip, without affecting the original productivity of the production line. The present invention not only performs the synchronous and continuous descaling for both obverse and reverse surfaces of the metal plate strips, but also meets the requirements for the plate surfaces in the following procedure.