The invention relates to the field of agricultural plant protection, in particular to a plant growth regulator and application. The active ingredients of the plant growth regulator include an active ingredient A and an active ingredient B. Specifically, the active ingredient A is 2, 4-difluorobenzoyl aminoisobutyric acid, and the active ingredient B is chitosan oligosaccharide, and the weight ratio of the ingredient A to the ingredient B is 1-40:20-2000. Compared with single agents, the plant growth regulator composition provided by the invention has more significant effect, and can enhance the stress resistance of crops, promote crop growth, increase crop yield, and improve the quality of crop fruits.