Abstract: The effects of EGTA, verapamil and trifluoperazine on ABA contents of organs and xylem sap pH of maize seedling under drought stress were studied. The results show that the xylem sap pH of maize under drought stress is increased after treated by EGTA, verapamil or trifluoperazine. When the maize is treated by EGTA or verapamil, the ABA contents of leaf, stem or root decrease and are not related to the ABA concentration in the sap whose changes are complex. After being treated by trifluoperazine, the ABA content in the root increases, but decreases in the leaf and the stem. At the same time, the ABA concentration decrea ses in the leaf sap, but ABA concentrations in the stem and leaf doesn't change obviously.