Abstract: This paper studied the effects of weak light(30%～35% light intensity of the control light intensity) on photosynthesis, transpiration and growth morphological indexes in seedlings of different peppers. The result showed that under weak light environment, net photosynthetic rate, transpiration rate and water use efficiency decreased. The decrease of net photosynthetic rate was considered as a result of non-stomata restriction. The synthesis and accumulation of assimilate were significantly inhibited under weak light. It can be seen that weak light led to the decrease of leaf numbers, root/shoot ratio, vital leaf mass, specific leaf mass, total dry mass and healthy indexes and the increase of plant height/stem diameter ratio. Under weak light the chlorophyll a/b ratio declined but the chlorophyll contents and leaf water content increased. Weak light-tolerance of hot pepper was generally stronger than sweet pepper. Pepper may possess potential weak light-tolerance which grown under weak light with higher relative healthy index and less decreasing net photosynthetic rate.