The aim of this study was to explore the root morphology and growth characteristics of Tamarix chinensis with different densities on the beach of the Yellow River Delta. Low-density (1100 trees/hm²), medium-density (4100 trees/hm²), and high-density (7100 trees/hm²) T. chinensis near Binzhou Port in Shandong Province were used as the research objects. The full excavation method was used to excavate the root systems of T. chinensis with different densities; then, indicators such as aboveground biomass, root biomass, spatial distribution characteristics, topological structure and connection length were measured and analysed. The results showed that (1) under the conditions of medium- and high-density forests, T. chinensis invested more in root growth to ensure the absorption and utilization of underground resources, with root to shoot ratios of 0.59 and 0.53, respectively. The root-to-shoot ratio of low-density T. chinensis was 0.44. (2) The relationship between the root and shoot growth of T. chinensis under the conditions of low-density and medium-density indicated allometric growth, and under the conditions of high-density, it grew uniformly. (3) The root growth of T. chinensis grown at different densities was mainly distributed horizontally, showing the characteristics of horizontal root type. The root width and lateral root length of medium- and high-density T. chinensis were smaller than those of low-density T. chinensis, and the roots of low-density T. chinensis had the largest horizontal distribution range, which is conducive to enhancing foraging and fixing ability. (4)The density of T. chinensis was significantly correlated with the topological index. The root topology of low-density T. chinensis tended to be dichotomous (topological index TI=0.62), whereas the topological structure of medium- and high-density T. chinensis tended to be herringbone-like(TI=0.86; TI=0.81). (5) The external connection length of T. chinensis roots with different densities was significantly larger than the internal connection length, resulting in the outward expansion of the T. chinensis root system. In conclusion, there were differences and similarities in the root and shoot allometric relationship, root morphology and growth characteristics of T. chinensis growing in different densities in coastal mudflats, showing different density adaptation characteristics. The root systems of T. chinensis with different densities were mainly distributed near the ground surface and expanded outward. Low-density T. chinensis expanded its root growth space mainly by increasing the number of branches; medium- and high-density T. chinensis had fewer branches and strengthen the use of internal resources to reduce competition with neighbouring plants. T. chinensis density was significantly correlated with soil moisture content, electrical conductivity, T. chinensis root depth, lateral root length and topological index.