Bupleurum chinense DC .and B .scorzonerifolium Willd are main species of Chinese traditional crude drug Chaihu. B . angustissimum (F ranch .)Kitagawa and B .sibiricum Vest are also locally used as Chaihu .The quantitative changes of the total saponins in the 4 plants are analyzed by TLC scanning method.T he results show that the contents of the total saponins of B .chinense and B . scorzonerifolium in autumn are a little to much higher than that in spring. Therefore a primary conclusion might be obtained that the best season for collecting Chaihu materials is in autumn.  Simultaneously the contents of the total sapo nins in B .angustissimum and B. sibiricum are obviously lower than that in B .chinense and B .scorzonerifolium , so selecting species with high content of saponins is one of the important factors for raising medicinal effect of Chaihu .