Purslane (Portulaca oleracea L.) is one of the valuable medical plants. Drought also is one of the most important environment stresses that influences metabolism and growth of plant. The studying of physiological plant response rather than water stress can be influential equipment for understanding drought resistance mechanisms. In this study, the drought stress effects on germination and physiological characteristic of the medical plant (purslane) were studied. Drought imposed on polyethylene glycol (PEG) seedlings and experiments were done in completely random model framework, with 3 replications. Polyethylene glycol stress was in seven levels involving blank (distilled water),-0.1,-0.2,-0.4,-0.6,-0.8 and-1 MPa. In relation to germination, meaningful difference was not observed between blank and the different levels (P<0.01); and the least rate of germination in stress level was-0.4 MPa) and the highest rate of germination in stress level was-0.2 MPa). Meaningful increase of proline and sugar synchronized with PEG concentration was observed in statistical level (P<0.01) with meaningful difference. In this, blank had the least rates and stress level of-1 MPa and the highest proline and sugar rates. Lipid content in purslane leaves with increasing stress level was decreased. In the highest lipid rate in stress level (-0.2 MPa) and the least concentration in stress level (-1 MPa), it was observed that this difference in P<0.01 was meaningful. The concentration of leave proteins with meaningful decrease (P<0.01) had the highest protein concentrations in blank and the least concentration in stress level was-1 MPa. In stress effect on leaf chlorophyll content, meaningful increase of chlorophyll a and b synchronized imposed increase of stress level. It was observed that with chlorophyll a the highest concentration in stress level was-0.6 MPa and the least concentration exists in blank; and also with chlorophyll b the stress level,-1 MPa had the highest and blank had the least concentration (P<0.01).