New zircon U-Pb age is obtained for late Early and Middle Triassic tuff layer from the Ganheqiao section, Wangmo County, Guizhou Province. The appearance of conodont Chiosella timorensis was discovered just 0.5 m below the tuff, which is used to define the Olenekian-Anisian boundary of the Lower/Middle Triassic. Twenty zircons defined a weighted mean 206Pb/238U age of (247.6± 1.4) Ma (2σ). The result defines a new dating for the regional stratigraphic correlation, and also provides a reliable dating for the duration of biological recovery in the Early Triassic after the extinction of Permo-Triassic.