Biological invasion has become the destruction of wetland ecosystem, and it is becoming more and more serious ecological problems. Alien invasive species can occupy a wide space in a short period of time and reproduce rapidly, which causes the changes in the characteristics and disappearance, and even extinction of local species. At last it would destroy the stability of the ecosystem. The invasion of Eichhornia crassipes in the wetland ecosystem results in the simplification and degradation of the aquatic plant community structure and function, which leads to the imbalance of the aquatic ecosystem and primary productivity decrease of submerged plant. Submerged plants are the important primary producers in many aquatic ecosystems, such as lakes and rivers. They play an important role in the health and stability of wetland ecosystems, and are also commonly used in wetland restoration projects. At present, there are some researches on the invasion mechanism of E. anemonis, but the effects of invasion degree on the growth and interspecies relationship of submerged plants Ceratophyllum demersum and Hydrilla verticillate are relatively lack. In this research, the effects of E. crassipes invasion degree on the growth and interspecific relationship of C. demersum and H. verticillata were explored in the control experiment. The results indicated that the biomass and branches of C. demersum and H. verticillata significantly decreased with the increase of the coverage of E. crassipes. The total biomass of submerged macrophytes was the greatest in the absence of E. crassipes. The interspecific competitive relationship between the two submerged plants was the strongest in the absence of E. crassipes, and with the coverage of E. crassipes rise, the relationship between the two submerged plants become competitive from week beneficial. H. verticillata had a significantly competitive advantage when they grew with C. demersum. Furthermore, the total nitrogen (TN) and total phosphorus (TP) contents in water were slightly decreased by the invasion of E. crassipes. Structural equation model (SEM) analysis results showed that plant invasion and water physical and chemical properties including TN and TP had a significantly negative impact on the growth of the submerged plants (P<0.05), the correlation between the physical and chemical properties of water and the growth of submerged plants was more significant. In conclusion, E. crassipes invasion degree significantly reduced the growth and reproduction of the two submerged plants. With the increase of invasion degree, the relationship between the two submerged species became from competition to assistance and then to competition. The results provide theoretical basis and technical support for the effective control of the invasion of E. crassipes and the restoration and reconstruction of submerged vegetation in wetland.