The invention relates to a method for improving the pinholes and levelling property of hydroxyalkylamide / polyester powder paint. After the existing hydroxyalkylamide / polyester powder paint is cured, pinholes are generated on the surface of the paint. The method comprises the following steps: firstly, adopting the highly branched polymer synthesis method and using isocyanate monomer and polyfunctional monomer to synthesize highly branched polyurethane solution; secondly, using water to precipitate the solution, performing suction filtering, drying to obtain highly branched polyurethane powder,mixing the highly branched polyurethane powder with hydroxyalkylamide / polyester powder paint according to a ratio, using a double-screw extruder to melt, extrude and tablet the mixture and obtain sheet, grinding the sheet to fine powder, and sieving to obtain the modified hydroxyalkylamide / polyester powder paint. By adopting the method, the problem that as the viscosity of the powder paint is increased too fast in the curing process, pinholes are generated, can be obviously improved, the curing speed can be reduced, the effect of high levelling can be realized and high thickness coating of the powder paint is easy to realize.