The invention relates to a hair growth liquid containing a dermal papilla cell-derived exosome and a preparation method thereof. The hair growth liquid comprises dermal papilla cell-derived exosome nanoparticles, a stabilizer, a humectant, a scalp absorption promoter, an antioxidant and water. According to the hair growth liquid, the exosome nanoparticles derived from the dermal papilla cells areused as main functional components, and a stabilizer, a humectant, a scalp absorption promoter, an antioxidant and the like are matched, so that the efficacy of the exosome nanoparticles derived fromthe dermal papilla cells can be maximized. According to the invention, the exosome is freeze-dried into powder, and then the powder is made into nano-particles to be applied to the hair growth liquid;according to the invention, high transdermal rate, good stability and good technical effect can be obtained through normal use; and the stabilizer and the scalp absorption promoter are added so as toprovide the synergistic effect with the exosome nanoparticles derived from the dermal papilla cells in increasing the transdermal rate and the stability. Compared with the common drug minoxidil in the prior art, the hair growth liquid has equivalent or better effects and high bio-safety.