The invention provides a left atrial appendage occluder and a using method thereof. The left atrial appendage occluder comprises an occluding disc and a fixed umbrella, wherein the occluding disc is connected with the fixed umbrella through a connection mechanism; the occluding disc is circular, water-droplet-shaped or oval; the fixed umbrella is petal-shaped; barb structures are arranged at the tail ends of petals; the connection mechanism is a rotating shaft, so that the occluding disc can rotate by taking the rotating shaft as a shaft. The using method of the left atrial appendage occluder comprises the following steps: firstly printing a thermal setting mold of the occluding disc by using a 3D printing technique according to the shape of the left atrial appendage, and thermally setting memory alloy wires which are woven into a cylindrical dense net into the occluding disc for occluding a left atrial appendage opening; secondly releasing the fixed umbrella and enabling the barb structures of the fixed umbrella to penetrate into the inner wall of the left atrial appendage; and finally pushing the occluding disc out of a conveying device and releasing the occluding disc, rotating the conveying device in a left atrium, then enabling the occluding disc to rotate relative to the fixed umbrella, and enabling the occluding disc to occlude the left atrial appendage opening. The left atrial appendage occluder is capable of reducing residual fistula.