The invention discloses a dual-roll continuous casting magnesium alloy thin plate rolling control method and a device. The method comprises that magnesium alloy solution is formed in an integrated casting and rolling machine; the temperature of a casting plate out of a casting roll is 300 DEG C to 500 DEG C and casting and rolling speed is 10m/min to 90m/min; the casting and rolling plate is cooled in oil with control temperature of 200 DEG C to 400 DEG C and plate-out thickness is 1mm to 4mm; uniform annealing disposal is carried out before the hot rolling of the casting and rolling plate; the front and the rear of a rolling machine are provided with heat preservation rolls for heat supplementation; finished magnesium alloy plate of 0.2mm to 1mm can be rolled in an annealing period. The device comprises an integrated casting and rolling machine, a continuous annealing furnace behind the casting and rolling machine, three four-roll hot rolling machines arranged in 90 DEG and heat preservation rolls at the front and the rear, a flying shear and an edge-cutting shear. By adopting casting rolling and rolling methods to produce the magnesium alloy plate, the invention has the advantages of short flow, low production cost, uniform composition of products, good surface quality and uniform mechanical performance in all directions. The method and the device can be applied to the production of the magnesium alloy and aluminium alloy thin plates in all series.