Abstract: After 3-year studies of population and physiological ecology in the field, the physioecological characters of transpiration of endangered plant Mosla Hangchowensis under controlled condition were studied. Results show that: 1 ) The peak height of the diurnal curves of the transpiration (Tr) decreased with the decrease of soil water content. 2) There was a negative regression between Tr and the air relative humidity in the soil of saturation and medium water content, and a positive regression in the dry soil. This indicates that M. hangchowensis bad the self-protection mechanism in the dry soil. 3) On fine clays with thin cloud and humid air or cloudy in midday, the daily Tr was lower (2.6 and 2.8 mol·g-1·d-1) than that on typical fine day(3.4mol·g-1·-1). 4) In shade(40% full sunlight) ,the mean Tr dropped by 76%, and the responds of Tr to temperature and relative humidity were little, but to FPD was bigger than that to full sunlight. 5) Under the condition of 15～18℃ ,the Tr was only correlated with soil water content among the ecological factors. M. hangchowensis has some physio-ecological characters which are usually found for mesic to xeric species. The physio-ecological mechanism by which M. hangchowensis could only occupy the existing ecological niche—thin soil on open sunny rocks and the reasons for the impossibility for the species to expand to thick soil habitat were put forwards.