The depth of groundwater can affect the root growth of plants. However, we know little about how groundwater depth influences the root growth characteristics and root architecture of Tamarix chinensis in the Yellow River Delta. To reveal the response law of the root growth characteristics of T.chinensis in the Yellow River Delta concerning groundwater depth and determine a suitable groundwater depth of T.chinensis, we conducted a greenhouse experiment to test the response of root growth characteristics of T. chinensis to the groundwater depth. We grew T. chinensis under seven groundwater depths (0, 0.3, 0.6, 0.9, 1.2, 1.5 and 1.8 m) with a saline water of 6 g/L. The results showed that in saltwater, the groundwater depth had significant effect on the growth of the T. chinensis root system by changing the soil water and salinity contents. When the groundwater depth was less than 0.6 m, the root length, root diameters, lateral root number, total biomass, lateral root biomass and root link length of T.chinensis were significantly decreased. The topological structure was dichotomous. While, the number of lateral roots, root diameters, the number of secondary lateral roots and fine root biomass of T. chinensis were the greatest at 0.9 m depth of groundwater. The topological structure transitioned from dichotomous to herringbone-like. The total root biomass, taproot biomass, first-order lateral root biomass and average length of links of T.chinensis decreased once the groundwater depth over 1.2 m, and the topological structure was herringbone-like. Thus, the root growth of T. chinensis is closely related to groundwater depth. T.chinensis root growth changed, and the configuration was adjusted to adapt to different soil water and salt and groundwater depth. At a shallow groundwater depth (≤ 0.6 m), the root growth of T.chinensis was suppressed but branching increased, and the biomass of various tissues and organs was altered to adapt to water and salt stress. The most suitable groundwater depth for the growth of T.chinensis was at 0.9 m. When the groundwater depth was more than1.2 m, the roots of T.chinensis grew downward mainly due to soil drought stress, which increased the length of root, thus improved the efficiency of resource acquisition. We conclude that the T.chinensis can adapt to groundwater depth by altering root growth and morphology. Therefore, the adaptability of T.chinensis root system to different groundwater levels is of great significance to the study of vegetation restoration and ecological restoration of coastal saline-alkali wetlands under different groundwater conditions in the Yellow River Delta.