The invention discloses a preparation method and a use of hyperbranched polyurethane. The preparation method comprises the following steps: reacting a solution obtained through dissolving polyol in asolvent with isocyanate under certain conditions, then rapidly dropwise adding a solvent solution of polyol B to the above obtained reaction product, performing a reaction for a certain period of time, performing a chain extension reaction by using isocyanate, and carrying out an end capping reaction by using polyol C to finally obtain the hyperbranched polyurethane having a large amount of terminal ortho-hydroxy groups. The product is a novel boron adsorption material with a hyperbranched skeleton and a large number of the terminal ortho-hydroxy groups, has strong selective adsorption to boron, has the advantages of excellent mechanical strength, excellent oxidation stability, excellent flexibility, excellent resilience, excellent oil resistance, excellent solvent resistance and especially excellent water resistance, and can be reused in the process of extraction of boron from salt lake brine, industrial wastewater and seawater.