The invention discloses a flowering branch pruning method of single-pole paeonia rockii. The method comprises the steps of lifting and excavating seedlings of the paeonia rockii, leaving a main pole,cutting off branches, conducting ultraviolet irradiation for 2-3 minutes, immersing the seedlings in a bactericide solution, after the bactericide solution is dried, immersing the seedlings with rooting powder, burying, conducting field planting, trimming, cultivating, and applying a fertilizer. The tree-shaped paeonia rockii obtained by the method has a thick stem, a large flower pattern, a beautiful flower color, a tree-like shape and a developed root system, is drought-resistant, has strong drought resistance, strong wind resistance, enhanced adaptability, controllable tree shape, long-lasting tree shape and enhanced ornamental performance, is precise in application of fertilizer raw materials and ratio after each pruning stage, has a long flowering period, and is suitable for factory cultivation.