The branch water potential, average tree height and basal diameter of P.×Xiaozhuanica young forest were determinated based on the water controlling experiment. The results showed that there was no significant change for the branch water potential of P.×Xiaozhuanica when the soil water content was higher than 15.6%, but the branch water potential decreased rapidly when the soil water content was less than 11.03%. The young forest grew normally and the growth amount increased significantly when the soil water content was higher than(17.71±2.75)%. However, the young forest showed up severe recession characteristics, nearly stop growing, and some of the tree even dying when the soil water content was below(7.12±2.75)%. Therefore, the perfect soil water content should be(17.72±2.75)% for the rapid growth and maintaining the stability of P.×Xiaozhuanica young forest.