Abstract: Two tea cultivars, Tieguanyin and huangdan, are the core parents used in oolong tea breeding. Many premium oolong tea cultivars have been bred from them. Using ISSR molecular markers, 9 primers with high polymorphism and clearly distinguishable ISSR amplified bands were selected for the amplification of 24 tea varieties (or lines) as well as the determination of the genetic diversity and relationship among the cultivars. A total of 73 bands was generated with 15 ISSR primers. Of which, 47 were polymorphic at a rate of 64.4%, averaging 5.2 bands amplified per primer. An analysis on the genetic similarity of the 24 tea cultivars yielded coefficients ranging from 0.644 to 0.889, with an average of 0.727. It suggested that the genetic bases of the germplasms were limited, and their genetic relationships close. The results would provide valuable information for tea breeding in the future.