In order to make an accurate investigation of walnut frost damage in time after late frost damage, provide accurate statistical data for yield estimation in disaster years, and provide theoretical basis for government departments to formulate control measures and walnut production and cultivation, an existing investigation methods of late frost damage of walnut were improved in this study. The investigation characters were clarified, the classification standard was unified, the sample data of late frost damage of walnut were processed, and the statistical analysis table of freezing damage traits was established. Then, the freezing damage index and freezing damage grade of the investigation characters were determined by using the preset standardized data as reference, which solved the problems on the disunity of the standards of the characters and grades of the frost damage, the poor operability of investigation methods, the subjective judgment of different investigators and the large error.