[Objective] In order to guide local afforestation and promote efficient use of water resources, the green water flow of the typical artificial forest of Robinia pseudoacacia, Platycladus orientalis and Pinus tabulaeformis was studied in the loess gully region.[Methods] The applicability of Granger model in typical artificial forest land in Nanxiaohegou sub-basin was evaluated. Then combined with the measured green water of low efficiency, the high and low efficiency green water in each forest was separated. And based on the separation results, we analyzed and summarized the characteristics of high and low efficiency green water changes in various forest land during the rain free period and their relationships with solar radiation, leaf area index, and soil moisture content.[Results] ① The Granger model has good applicability in various forest lands, and its Nash efficiency coefficient was above 0.67 and 0.52 in the regular period and verification period. ② In each forest land, the change of high efficiency green water in different hydrological years was Platycladus orientalis (45.93%) > Pinus tabulaeformis(28.81%) > Robinia pseudoacacia (6.11%). The change of low efficiency green water is Pinus tabulaeformis (52.73%) > Platycladus orientalis (34.97%) > Robinia pseudoacacia (21.16%). And the change of green water flow was Platycladus orientalis (21.13%) > Robinia pseudoacacia (12.37%) > Chinese pine (0.50%). Robinia pseudoacacia, Platycladus orientalis and Pinus tabulaeformis forest land with 10 cm relative water content less than 50% were 90.1%, 56.8%, 64.0% during dry year, and 68.4%, 70.1%, 71.2% during extremely dry year; 20 cm relative water content less than 50% are 90.1%, 61.0%, 60.1%, and 80.0%, 66.7%, 50.5%.[Conclusion] ① Platycladus orientalis was the most sensitive tree species for water. ② Different hydrological years have a greater impact on the high efficiency green water (45.93%) of Platycladus orientalis than the low-efficiency green water (34.97%), and the opposite was true for Robinia pseudoacacia and Pinus tabulaeformis. ③ Solar radiation had the greatest impact on the low efficiency green water in Platycladus orientalis, and the greatest impact on the high efficiency green water in the Robinia pseudoacacia forest. The low efficiency green water of Robinia pseudoacacia and Pinus tabulaeformis decreased with the increase of leaf area index while the high efficiency green water increased. The high-efficiency green water of Platycladus orientalis was less affected by the leaf area index. The three forest land was in a state of moderate water shortage during most of the experiment period.