Abstract: The determination of germinability of Pinus massoniana and Pinus sylvestris var. mongolica by IDX method was studied. The seeds were soaked in water for 16h and incubated at 15 ℃ for 56h with relative humidity close to 100％. The seeds of two species were dried in a rotating (6 r./min) net-drum at 15 ℃(40％　RH） for 3h and 2h respectively. X-radiograph of seeds was taken. The viable seeds show low optical density on the radiographic image because they have higher ability to remain the water content absorbed, and there is no optical density difference or very weak delimitation between embryo, gametophyte and seed coat for viable seeds on the radiographic image, vice versa.