We observed mating behavior of the Northern Grass Lizard (Takydromus septentrionalis) in an outdoor enclosure with aims to define the ethogram of mating behavior patterns and to determine the relationship between reproductive success and individual phenotypes in males.The general pattern of mating behavior in T.septentrionalis was:approaching → tail-biting → belly-biting → copulation.Duration of each behavior was 0.53 min,1.77 min,0.47 min and 141.3 min,respectively.Seventy percent of males that successfully mated were with greater mean snout-vent length and body mass than that of females.The mating success of males was positively correlated with their body size,but with their head size (length and width),tail length,body mass or skin color.