Salt-affected soils may retard plant growth and cause metabolic alterations. The objective of this study was to investigate the effect of salinity in deep soil on root growth and metabolic changes of tall fescue (Festuca arundinacea). Tall fescue seeds (cv. Houndog V) were planted in polyvinylchloride (PVC) tubes (9 cm diameter × 45 cm long) for 2 months with three treatments of growth substances: (1) control, filled with peat-sand mixtures for full tubes (40 cm height, sand:organic fertilizers = 7:3, w/w); (2) T20, 20 cm saline soil covered with 20 cm organic fertilizers and sand; (3) T30, 30 cm saline soil covered with 10 cm organic fertilizers and sand. Turf quality and vertical shoot growth rate (VSGR) significantly decreased in T30, but not for T20, when compared with the control. Salinity in deep soil obviously inhibited the root growth as indicated by the lower root length, root projected area, root diameter, root fresh, and dry weight, but increased the level of amino acids (Asp, Glu, Ser, Gly, etc.) and soluble sugars (glucose, fructose, sucrose). Root activity in top layer (0–10 cm) of saline soil increased while decreased in deeper layer (20–40 cm) when compared with the control. The increase of root activity and free amino acids in roots from upper layer and the accumulation of soluble sugars in roots from deeper soil layer under salinity conditions were the adaptive responses and regulative mechanisms that for supporting the above-ground plant growth in tall fescue when exposed to deep soil salinity conditions. These results also suggested that a 20 cm of improved mixture of organic fertilizers with sand on the top of saline soil could be sufficient to supply basic space for the normal growth of turfgrass with regular spray irrigation.