The invention provides a multiple quantum well light emitting diode and a preparation method thereof. A multiple quantum well active layer includes alternately overlaid well layers and barrier layersof multiple periods sequentially growing from bottom to top, wherein each well layer is formed by an InGaN material, each barrier layer further includes a periodic structure composed of a first GaN layer, a P-type AlGaN layer and a second GaN layer, the first-fourth layers of the barrier layers include one above-mentioned periodic structure, the fifth-eighth layers of the barrier layers include two above-mentioned periodic structures, and the ninth-last layers of the barrier layers include three above-mentioned periodic structures; the barrier layers effectively reduce electron overflow, improve hole injection and transmission efficiency, avoid growth defects, and effectively improve quantum efficiency of a quantum well, thereby improving the luminous efficiency of the light-emitting diode.