[Objective] The variation characteristics of 0—300 cm soil water content of urban garden green space in the Guanzhong area were studied to determine the variation characteristics of evapotranspiration and its components in an urban garden green space in order to provide a scientific basis for efficient urban water management. [Methods] We used Ginkgo biloba as an example, soil moisture of a garden green space with G. biloba as the main scenic tree was measured with a neutron moisture meter. The sap flow rates for G. biloba trunks of 24 and 29-year old trees was monitored with thermal diffusion probes in 2020. Soil evaporation between trees was measured with micro-evaporating dishes, and evapotranspiration and its components were calculated. [Results] The variation of 0—300 cm soil water content in the two green spaces was basically moderate. The transpiration range of 24-year old G. biloba green space was 0.24~9.06 mm/d, and transpiration accounted for 51.77%~71.92% of evapotranspiration. The respective ranges in the 29-year old green space were 0.46~19.76 mm/d and 64.45%~79.24%. [Conclusion] In an urban ecosystem, the largest component of evapotranspiration of G. biloba green space of different tree ages was transpiration, and transpiration accounted for the largest proportion from July to August. There was no obvious relationship between soil water environment change and tree age, and the correlation with tree evapotranspiration was weak.