Abstract: To study the effect of drought stress on coniferous seedlings, using 2 years seedlings of Larix principis-rupprechtii and Pinus tabuliformis as test materials, drought stress experiments were conducted using a field simulating method, by analyzing and comparing the changes of chlorophyll a, chlorophyll b, chlorophyll a b contents and the value of chlorophyll a/b as well as root activity. Results showed that: (1) The contents of chlorophyll a, chlorophyll b, chlorophyll a b appeared a trend of rise first and then fall under the drought stress in L. principis-rupprechtii, but in P. tabuliformis it always decreased. It decreased continuously in L. principis-rupprechtii and fluctuated within a small range in P. tabuliformis which was the value of chlorophyll a/b; (2) Meanwhile, it displayed the same trend, which the root water content declined throughout and the root activity enhanced firstly and then weakened, between the two tested species under drought stress. (3) In addition, the chlorophyll a b contents had significantly positive correlations with root activity in L. principis-rupprechtii, but there was no significant correlations, only had an increased trend in P. tabuliformis. Through comprehensive analyses combined with the drought resistance performance of plants, it was concluded that the seedlings of L. principis-rupprechtii was more sensitive than P. tabuliformis. But it had lower adaptability and drought resistance performance than P. tabuliformis.