The invention discloses a magnesium-alloy sectional-material high-temperature prestretching rapidly heating system.The magnesium-alloy sectional-material high-temperature prestretching rapidly heating system comprises a low-voltage direct-current large-current power source, a wire, clamps, a thermoelectric couple, heat preservation chambers and lifting brackets.A positive pole and a negative pole of the low-voltage direct-current large-current power source are connected with the two ends of a magnesium-alloy sectional material through the wire and the clamps to form a loop; the thermoelectric couple is inserted into the heat preservation chambers and in close contact with the magnesium-alloy sectional material; the heat preservation chambers are fixed on the lifting brackets, and the lifting brackets lift through a hydraulic device.According to the magnesium-alloy sectional-material high-temperature prestretching rapidly heating system, the low-voltage direct-current large-current heating technology is adopted, a large current directly passes through the magnesium-alloy sectional material, the resistance of the magnesium-alloy sectional material is used to cause the Joule heating effect, rapid temperature rising is achieved, the heating temperature can be selected at the temperature of 90 DEG C-300 DEG C, the heating time can be controlled 0.5 min-15 min.The magnesium-alloy sectional-material high-temperature prestretching rapidly heating system is simple in structure and convenient to use, the sectional material can be evenly heated to the high temperature in a short time, the magnesium-alloy sectional material is prestretched at the high temperature, and therefore fracture is avoided to obtain the large prestretching amount.