Abstract: This thesis aims to study the flowering rule and predict the flowering time of Citrus grandis ‘Tomentosa’, thus to provide a meteorological service basis for ornamental activities of C. grandis‘Tomentosa’ cultural festival. The correlation between the initial flowering period of C. grandis‘Tomentosa’and meteorological factors was analyzed by using the phenological observation data of C. grandis‘Tomentosa’from 2012 to 2018 and the meteorological observation data of the same period, and the prediction model of the initial flowering period of C. grandis‘Tomentosa’was established. The results showed that the initial flowering period of C. grandis‘Tomentosa’had a high correlation with temperature, sunshine, rainy day and maximum temperature in certain months. The surface average temperature (X1) in January had the greatest influence on the initial flowering period of C. grandis‘Tomentosa’, followed by sunshine hours (X2) in October last year and the average minimum temperature (X3) in late January. By stepwise regression method, the prediction model of the first flowering period of C. grandis‘Tomentosa’was obtained: Y=122.0427- 2.9445X1- 0.1341X2- 0.7358X3. Using this model, the initial flowering period of C. grandis‘Tomentosa’was measured, the error was 0- 1 day, and the accuracy was high. The initial flowering date of C. grandis ‘Tomentosa’ in 2018 was predicted. The difference between the predicted value and the observed value was 1 day, and the predicted value was basically consistent. The established prediction model can accurately predict the initial flowering period of C. grandis‘Tomentosa’in Huazhou.