[Objective] The invasion of Trifolium repens have occupied the living space of turfgrasses and seriously have threatened the quality and function of turfs. To clarify the impact of T. repens invasion on the functional traits of Poa pratensis and turf quality, which can provide a theoretical basis for further understanding the invasion mechanism of T. repens and the establishment and maintenance of gramineous turfgrass. [Methods] Taking the T. repens invasion of P. pratensis turf as the research object, the sample survey method was employed to investigate the differences in the functional traits and turf quality of P. pratensis under different invasion degrees of T. repens （control and low invasion, moderate invasion, heavy invasion）, and to comprehensively evaluate the turf quality under the degrees of invasion by the membership function method. [Results]（1）With the increase of the degree of T. repens invasion, the carbon content of each organ of P. pratensis, the cost of leaf construction, and the ratio of carbon to nitrogen, carbon to phosphorus, nitrogen to phosphorus gradually decreased, while the specific leaf area, nitrogen and phosphorus content of each organ increased. （2）At the same level of invasion, the carbon, nitrogen and phosphorus contents of each organ of P. pratensis were greater in leaves than in roots and stems, and the carbon to nitrogen rations and carbon to phosphorus ratios were greater in roots and stems than in leaves, while the nitrogen to phosphorus ratios were greater in stems and leaves than in roots. （3）The density, texture, greenness index and uniformity of P. pratensis turf decreased with the increase of T. repens invasion, while the aboveground biomass and belowground biomass increased. （4）The results of the comprehensive evaluation of the membership function method showed that the turf quality was the best under no T. repens invasion, and the worst under T. repens heavy invasion, and the leaf carbon content had the greatest influence on the turf quality. [Conclusion] The invasion of T. repens changed the functional traits of P. pratensis, reduced the turf quality in the invaded area, and seriously affected the landscape and function of the turf.