The effects of leaf water potential(LWP) and the variations of soil-plant-atmosphere continuum(SPAC) water potential gradient are analyzed by studying the dynamic changes of the LWP in Qinghai alpine semi-arid area.Results show that the pre-dawn and evening LWP is high,while the minimum peak value is observed at about 13 o'clock.The daily average LWP in June is the lowest during the whole growing season.The study also shows that the LWP has significant correlations to air temperature,photosynthetic active radiation,and humidity under the condition of full irrigation,while there is a remarkable positive correlation between the LWP and the soil water content(SWC) when soil water is restricted.With the ascendant order of soil,leaf,and atmospheric water potentials in SPAC system,a water potential gradient is created.Meanwhile,the correlation between the pre-dawn LWP and the SWC is higher than that between the LWP and atmospheric water potential in the whole growing season of Caryopteris mongolica Bunge.