The traits of root xylem play important roles in plants through the provision of structural support, nutrient uptake, and water transport. However, the relationship between root hydraulic traits and plant growth performance in drylands remains unclear. In this study, the growth performance and hydraulic traits of 35 perennial forbs on the Loess Plateau were obtained through field surveys and xylem anatomy experiments. The results revealed that plant growth performance was significantly correlated with xylem anatomical traits. The vessel fraction (VF), mean vessel area (MVA), theoretical hydraulic conduction diameter (Dh), and mean water transfer efficiency (MKp) increased with the age of perennial forbs. Higher Dh, MVA, and MKp were observed to increase the growth rates and the heights of main stems, which were virtually unaffected by the vessel number (NV). Since MVA, Dh, MKp, and NV were important for the growth rate, hydraulic traits were more reliable predictors of the growth rate. This study revealed that the hydraulic traits of taproots significantly influenced plant growth performance, especially in drylands. Further, we highlighted the relationships between the hydraulic traits of roots and plant growth performance, which provided insights into survival strategies and management strategies for vegetation growth in water-limited regions.