Sediment accretion and drought often occur concurrently in floodplain wetlands, and both affect plant growth and distribution. However, the combined effects of these two factors remain poorly understood. In this study, we examined the effects of water levels (0 cm，?20cm，and?40 cm) and sediment burial depths (0 cm，3 cm, and 6 cm) on the growth of Phalaris arundinacea L. within populations of the dominant species Carex thunbergii Steud. (1 P. arundinacea : 25 C. thunbergii individuals) in the Shengjin Lake wetland. Upon high sediment burial (6 cm), a reduction in the water level from 0 cm to -20 cm significantly increased the biomass, plant height, and root length of P. arundinacea (P < 0.05) , but significantly reduced the plant height of C. thunbergii (P < 0.05). This indicated that moderate drought enhanced the growth of P. arundinacea upon high sediment burial. Under moderate drought (?20 cm), an increase in sediment burial from 0 cm to 6 cm significantly increased the aboveground biomass of P. arundinacea (P < 0.05), but significantly decreased underground biomass of C. thunbergii (P < 0.05). In addition, moderate drought and high sediment burial increased the aboveground biomass ratio of P. arundinacea within total aboveground biomass (C. thunbergii + P. arundinacea) (P < 0.05). These results suggested that moderate drought combined with high sediment deposition may enhance the growth of P. arundinacea within C. thunbergii grasslands. Management measures such as water level regulation and sedimentation alleviation may help maintain the structure and function of wetland vegetation.