Abstract: The distribution characteristics of water potential and drought tolerance of soybean,poanut,corn and sweet potato are analyzed with SPAC theory.The results show that the leaves water potential of crops is a physiological index reflecting the water content of crops,the difference of water potential between roots and leaves of corn is 0.293MPa and that among leaves is 0.067MPa.The leaves water potential is outstanding among different crops,that is more high and crops drought tolerance is more strengthened.