To explore the eco-physiological adaptation of Sabina vulgaris to drought stress, a drought-controlled experiment was performed using PEG (Polyethylene glycol) with three levels of osmotic potential (0.02, -0.1 and -0.34 MPa, respectively) in the culture solution in the greenhouse for 6 years (1997-2003). The seasonal changes of photosynthetic characteristics and pigment composition were investigated for the whole year in 2003. The pattern of seasonal change in stomatal conductance was shown in bimodal distribution with peaks in both May and September in 2003, and the stomatal conductance in the control was much higher than that of the other two water stress treatments, while the photosynthetic rate of low water stress was the highest among the three treatments. The ratio of chlorophyll a to chlorophyll b (Chl a/b) increased for all three treatments through November to March next year, particularly at the high water stress condition. The total leaf Chl content (Chl a+b) increased for all the three treatments through March to September, and the value was the lowest with the high water stress treatment. The total xanthophyll content (V+A+Z) and (A+Z)/(V+A+Z) were significantly higher in winter (November to March) than in summer (May to July) compared to that in other seasons, which was particularly obvious with high drought treatment.