Abstract: The activation agents were used to treat water-soluble phosphate and be compound to expert fertilizers of Citrus grandis Osbeck and their field biological effect and mechanism were studied on the produce terra of Citrus grandis Osbeck in Meizhou of Guangdong.The results are as follows: (1) The P nutrition of leaves at every growth period of the tree were improved,accordingly the yield and the quality of Citrus grandis were increased markedly when the special fertilizers contained activated phosphate were used to the produce terra of Citrus grandis in Meizhou.(2)The Fe and Mn elements in the lateritic red earth derived from arenaceous shale are closely correlated to the efficiency of P elements. Si can benefit the release of P in soil,and proper Ca also increase the activity of P element.(3)The activation agents can control the release of water-soluble P so as to stabilize the P supply from soil. (4)The lateritic red earth derived from arenaceous shale is the same basalt-latolol soil of other zonality and other mother material as the control mechanisms of activation agents to P is to adjust the contents of Fe,Al and Mn in soil so as to realize the activation of P in soil-plant system.