Abstract: In order to supply the scientific support for cultivation and management of Toona ciliata Roem. by studying on water physiology of young Toona ciliata Roem. clones seedlings, the author set up different drought stress treatments to find out the response of drought stress on relative water content of leaf and cholorophyll content of 5 1-year old young Toona ciliata Roem. clones seedlings. The results showed that: (1) severe stress (17 d continuous water break) resulted in the occurrence of the lowest relative water content of leaf of young Toona ciliata Roem. clones seedlings. There was no significant difference in relative water content of leaf among clones. For the unstable weather condition, the periodic change rule of relative water content of leaf of young Toona ciliata Roem. clones seedlings was not obvious. (2) Severe stress (17 d continuous water break) resulted in the occurrence of the highest cholorophyll content of young Toona ciliata Roem. clones seedlings. There was no significant difference in cholorophyll content of leaf among clones. There was a periodic increase trend in cholorophyll content of leaf of young Toona ciliata Roem. clones seedlings.