Frost is one of the major meteorological disasters in Ningxia, which has a significant impact on the apple blossom to young fruit stage and has become a limiting factor for the development of the apple industry in Ningxia.n this study, the flowers and fruits of two main apple varieties 'Gala' and 'Fuji' in Ningxia were used as test materials in the bud, blossoming, fruiting and young fruiting period, and the natural cooling process was simulated by using a field frost tester to statistically measure the freezing rate, and then the Logistic equations were set up with the freezing rate of 20%, 50%, and 80%, and the critical temperatures for light, medium, and severe freezing were determined.We also tested the cold resistance indexes such as overcooling point, freezing point, conductivity, soluble sugar and soluble protein of each variety in different phenological periods, and combined with the multiple linear regression method to comprehensively judge the main influencing factors of the difference in cold resistance from apple flowering to young fruiting period.The results showed that: (1) the cold resistance of 'Gala' was stronger than that of 'Fuji' in all periods; (2) the cold resistance of the same apple variety was different in different phenological periods, which was manifested as follows: bud period＞blooming period＞fruiting period > ＞young fruit period. (3) The freezing threshold temperatures of the two apple varieties in each period were mild, moderate and severe, and their freezing threshold temperatures showed an increasing trend as the seasonal period progressed. (4) The freezing rate was highly significantly and positively correlated with the half-lethal temperature with a correlation coefficient of 0.909, and highly significantly and negatively correlated with the soluble protein content with a correlation coefficient of 0.874. The study showed that the four phenological periods of 'Gala' and 'Fuji' were highly significant in terms of conductivity and soluble protein content had a strong response relationship to the freezing rate of ovary, and the temperature of overcooling point and freezing point also had a certain response to the freezing rate of ovary, which can be used as important indexes for evaluating the cold-resistant traits of apple, such as conductivity, soluble protein, overcooling point and freezing point.