A low-viscosity and solvent-free polyurethane adhesive was prepared with mixed polyester, polyether and IPDI as main raw materials. The influences of different moral ratios of polyester and polyether on reaction time, viscosity and water resistance, adhesive strength were researched. The effects of catalysts to adhesive were well discussed. The experimental results showed that polyurethane adhesives composed by mixed polyester and polyether had low viscosity and had better waterproof quality. The adhesives showed the best comprehensive properties when the mole ratio of OHs of polyether to OHs of polyester was 0.3/0.7. Catalysts added to this adhesive could speed the curing reaction, but it reduced the peel strength of the adhesives.