The study aims to investigate the effect of air temperature on growth date(bud bursting, flowering, blooming) of Citrus Unshiu in Jeju and Seogwipo, and estimate future growth date using air temperature data and growth date of Citrus Unshiu from 1998 to 2015. The trend and relationship between growth date of Citrus Unshiu and air temperature in Jeju and Seogwipo are analysed. As a result, The trend of growth date of Citrus Unshiu is delayed during study period. The correlation between Citrus Unshiu growth date and air temperature is negative. It means that air temperature related to the growth date of Citrus Unshui is decreasing. Future growth date of Citrus Unshiu is estimated to be earlier by future climate change scenarios. Air temperature expect to rise, but it can appear the low air temperature to be able to hurt citrus tree.