Abstract: Abstract: The aims of this study were to find the genetic mechanism of cold tolerance in zoysia grass, and to provide an experimental basis for analysis of molecular markers related to cold tolerance for Molecular Marker-Assisted Breeding of zoysia grass. Two Zoysia F₁ segregating populations of the reciprocal crosses of Z136 (cold tolerant) and Z039 ( non-cold tolerant) were obtained, and the cold tolerance of F₁ populations were identified by leaf electrolyte leakage rate. The heredity of cold tolerance in the two F₁ populations of Z136×Z039 and Z039×Z136 were analyzed by major gene and polygene mixed genetic models. Both crosses had a high variation range of cold tolerance: -11.6 to -0.3℃ (Z136×Z039) and -10.9 to -1.7℃ (Z039×Z13), ranges far beyond those of their two parents (-9.1 and -3.3℃). The average LT₅₀ of reciprocal crosses were -6.0 and -6.3℃, both intermediate between the two parents. No obvious maternal genetic phenomenon for cold tolerance were observed in zoysia grass. The frequency distribution of cold tolerance in F₁ populations of the two crosses showed characteristics of a mixed normal distribution, which indicated that the inheritance of cold tolerance was based on a major gene plus poly-genes model. The results of genetic analysis showed that genetic model B-4 was the most suitable for the trait, i.e. the cold tolerance of zoysia was controlled by two equal additive major genes and the heritability of the major genes were 77.27% and 79.60% in the two crosses.