The invention provides a plant growth regulator, a preparation method thereof and an application. The plant growth regulator comprises the following components by weight percent: 0.001 to 0.01 percent of brassinolide, 0.01 to 0.1 percent of S-abscisic acid, 1.0 to 3.0 percent of 95% sodium diethylhexyl sulfosuccinate and maple leaf extract alcohol solution supplemented to 100 percent. Various components of the plant growth regulator are synergistic, so that the absorption effect of a plant is greatly improved, the effect of promoting the maturity of fruits and improving the color, a sugar degree and appearance gloss are remarkable, the preparation method is simple, and the market development prospect is vast.