The disclosure discloses a dendritic polyethylene glycol derivative and a preparation method and an application thereof. The dendritic polyethylene glycol derivative has a structure of formula (I), has multiple end functional groups, has a stronger water solubility in comparison with linear-chain polyethylene glycol, and can solve a problem of insufficient water solubility due to the increase of load when modifying an insoluble drug by the polyethylene glycol. The preparation method of the dendritic polyethylene glycol derivative provided by the disclosure has mild reaction conditions, is green and environmentally friendly, is low in cost, and is easy to implement industrialization.