Abstract: 【 Objective 】 In view of the problem that it is difficult to monitor accurately the water deficit of jujube in Aksu area, this paper aims to suggest that the canopy-air temperature differential is taken as the index of water deficit, which has certain guiding significance for the follow-up follow-up irrigation research of Aksu jujube. 【 Method 】The canopy-air temperature differential of jujube at different growth stages was measured by infrared thermometer, combined with the collected relative soil water content (RSW), crown net radiation value (Rn), wind speed (V), air temperature (Ta) and humidity (RH), the relationship between canopy-air temperature differential of jujube and soil moisture and meteorological factors were explored based on Penman's formula, and the canopy-air temperature differential corresponding to the upper limit of soil relative water content suitable for jujube trees in each growing period was taken as the judgment index of water deficit. 【 Result 】There was a single peak parabolic relationship on sunny days, and a multi-peak curve relationship on cloudy days, the absolute value of canopy-air temperature differential in cloudy days was significantly lower than that in sunny days,ΔT peak appears between 13:00 and 14:00; multivariate linear regression analysis of ΔT and RSW, Rn, V, Ta and RH shows that RSW and Rn were significantly correlated, but other factors were not significant; regression model expression considering RSW and Rn was ΔT=4.8-11.7RSW+0.003R_n, regression model expression considering RSW only was ΔT=5.5-12.2RSW .【 Conclusion 】The critical canopy-air temperature differential of jujube trees in Aksu area was -2.43℃ at germination and leaf development stages, -3.04℃at flowering and young fruit expansion stages, and -1.82℃ at fruit ripening stage, irrigation was needed when the measured canopy temperature difference was higher than the critical canopy-air temperature differential of the corresponding growth period on sunny days at 14:00 noontime.