The invention relates to a multi-stage fracturing sliding sleeve device and a using method thereof. The multi-stage fracturing sliding sleeve device is characterized by comprising an upper pipe column joint, a sleeve body, a lower pipe column joint, a switch sleeve and a reducing tee, wherein the lower part of the upper pipe column joint is connected with the upper part of the sleeve body; the lower part of the sleeve body is connected with the upper part of the lower pipe column joint; the sleeve body is in a circular barrel shape; a plurality of side holes are formed at the circumference near the upper position of the sleeve body at intervals; a circle of steps are formed at the inner side near to the lower position of the sleeve body; the switch sleeve which is also in a circular barrel shape is arranged in the sleeve body and below the upper pipe column joint and is fixed with the sleeve body through a plurality of pins; the inner diameter of the lower part of the switch sleeve is larger than that of the upper part of the switch sleeve; the reducing tee is arranged at the inner lower part of the switch sleeve; the circumference of the upper part of the reducing tee is fixedly connected with the switch sleeve through the plurality of pins; a plurality of cutting slits are formed at the lower part of the reducing tee; sealing mediums are filled in each cutting slit; the top of the lower pipe column joint is in a taper shape; a circle of steps bulging inwards are arranged at the bottom of the reducing tee, and the outer diameter of the top of the lower pipe column joint is smaller than that of the bottom of the reducing tee.