The invention discloses a preparation method of a urea modified polyether polyatomic alcohol, which is that organic solvent, urea, emulsifier, polyether polyatomic alcohol are evenly mixed and heated up to 130-140 DEG C, isocyanate is added to react for 0.05-1.5 hours, so as to obtain urea-isocyanate emulsion; polyether polyatomic alcohol and micro-modular active hydrogen agent is added to the urea-isocyanate emulsion to react 0.1-2 hours under 80-140 DEG C continuously, so as to obtain the urea modified polyether polyatomic alcohol after the removal of the solvent by vacuumizing under 100-140 DEG C. The method is characterized by rapid aggregate velocity, high production efficiency, simple operation synthetic process, easy control, good reproduction quality and lower production cost without needing the device that is specially used. The modified polyether polyatomic alcohol obtained by the method has stable property and good reproduction quality.