The invention discloses polypeptides and biological application for improving the proliferation efficiency of umbilical cord mesenchymal stem cells. A preparation method of the polypeptides comprisesthe steps that 1, enzymolysis is conducted on calendula officinalis seeds, enzymatic hydrolysate is contained in a dialysis bag with the molecular weight cutoff of 7000 Da for dialysis, and the watersolution, with the molecular weight cutoff less than 7000 Da, outside the dialysis bag is concentrated and freeze-dried to obtain freeze-dried polypeptide powder; 2, preliminary separation and purification are conducted on the freeze-dried polypeptide powder by using DA201-C macroporous resin, gradient elution is performed by using 30% ethanol, 45% ethanol, 60% ethanol and 75% ethanol sequentially, different gradients of elution are conducted on 3BV, all gradient eluants are collected, and concentration and freeze-drying are performed to obtain crude products F40, F50 and F70; 3, purificationis performed based on a gel filtration chromatography, wherein according to flows corresponding to chromatographic peaks having highest absorbance in a chromatogram collection sample solution, and thepolypeptides F40, F50 and F70 are obtained through freeze-drying. The polypeptides can remarkably improve the proliferation rate of umbilical cord mesenchymal stem cells and can be used for quick proliferation of the umbilical cord mesenchymal stem cells.