To explore the effects of planting salt-tolerant forage grass varieties on improving saline soil under the subsurface pipe in agro-pastoral intertwined zones, field experiments were carried out in Hongwei Experimental Base of Hetao Irrigation District in 2020 and 2021. The experiment consisted of five different treatments. It included Medicago sativa (TM treatment), Sorghum bicolor (TB treatment), Sorghum sudanense (TS treatment) and vacant land (T treatment), and the blank plot as the control (CK treatment). The results showed that the average bulk density of TM treatment was 1.416 g/cm3 in 0~60 cm soil layer in two years, which was decreased by 9.4% compared with that of CK treatment (P<0.05). It improved the salinity soil porosity under subsurface pipe for planting the three kinds of forage grass. The average porosity of 0~60 cm soil layer was increased by 10.3%~24.3% (P<0.05). And Medicago sativa treatment was the highest, 51.6%, after two years of experiment. The content of soil organic matter (SOM) in each treatment was gradually decreased with the increase of soil depth. The loss of organic matter in 0~60 cm soil layer treated by tube T alone was serious, and the average loss in two years was reduced by 20.3% (P<0.05). However, planting forage grass under subsurface pipe could effectively alleviate the loss of SOM. The treatment effect of Medicago sativa (TM treatment) was better, and the average organic matter content in soil layer was increased by 5.0% (P<0.05). The biomass fresh weight of three forage species under subsurface pipe was increased by 24.6%~49.2% in 2021 compared with that in 2020 (P<0.05). Medicago sativa had better effect on increasing fresh production. In conclusion, it had better effect on improving the saline soil under subsurface pipe for planting Medicago sativa (TM treatment). It improved the physical and chemical properties of saline soil and increased the content of SOM. It also achieved the objective of improving forage yield. The research result can provide theoretical basis and technical support for the implementation of subsurface pipe project and biological improvement of saline soil in Hetao Irrigation District.