Research the characteristics of sap flow velocity and it response to environmental factors in plantations with different degrees of degradation is helpful to reveal the mechanism of forest degradation, so as to provide scientific basis for structural adjustment and management of regional plantations. Taking Robinia pseudoacacia plantation in in the Yellow River in Ningxia as the research object, the sap flow rate and environmental variables of Robinia pseudoacacia in different degraded woodlands were monitored and measured from May to October 2022, and the response relationship between the sap flow rate and environmental variables of non-degraded Robinia pseudoacacia plantation (NDPP), moderately degraded Robinia pseudoacacia plantation (MDPP) and severely degraded Robinia pseudoacacia plantation (HDPP) was studied. The results showed that: (1) The daily average sap flow of NDPP, MDPP and HDPP respectively were 2.32 cm?h-1, 0.84 cm?h-1 and 0.45 cm?h-1; (2) With the aggravation of degradation, the response threshold of Robinia pseudoacacia sap flow rate to atmospheric temperature and saturated water pressure deficit increased, while the response threshold to solar radiation decreased. The critical thresholds of Robinia pseudoacacia sap flow rate with different degradation degrees were 29.6°C, 30.3°C and 32.7°C respectively, 1.14 kPa, 1.93 kPa and 2.39 kPa respectively and 428 W?m-2,314 W?m-2 and 222 W?m-2 respectively. (3) The sap flow rate of Robinia pseudoacacia decreased significantly with the decrease of soil water content, and the sensitivity of sap flow rate to the change of soil water content decreased with the aggravation of degradation; (4) The contribution of environmental variables to the sap flow rate of Robinia pseudoacacia with different degradation degrees is different. With the aggravation of the degradation degree of Robinia pseudoacacia in woodland, the total effect of solar radiation, saturated water vapor pressure deficit and soil moisture on the sap flow rate decreases. For the degraded Robinia pseudoacacia forest, appropriate thinning can be used to reduce stand transpiration, improve rhizosphere soil moisture environment, and then increase the sensitivity of trees to drought environment.