In order to study of drought stress in four sainfoin species (Onobychis Spp. ), a factorial experiments was conducted based on completely randomized design with four replications in glasshouse condition in research institute of forest and rangelands, Tehran, Iran in 2015. The factor A was four species as: O. michoxii O. cristagalli, O. sativa and O. sabnitens and factor B was four levels of drought stress: 100% field capacity (FC) as control, 75% FC, 50% FC and %25 FC. Seeds were sown in the pots and irriation was conducted based on drought stress levels. After 45 days from sowing date, data were collected for seedling fresh and dry weight, physiological traits as: chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, proline, water soluble carbohydrate, relative water content (RWC) and analyzed using SAS9 software. The results of analysis of variance showed significant effects of species, drought stress, and species by drought interaction (P<0. 01) for all traits except chlorophyll a. According to the results, seedling fresh and dry weight decreased by increasing of drought stress, while chlorophyll a and RWC increased. Overall, O. michoxii with higher values of chlorophylls, carotenoids, water soluble carbohydrate and seedling weight was more tolerant to drought stress, followed by O. sativa. These two species were introduced as relatively drought tolerant species.