The available phosphorus waas extracted with 2% of citrie acid from 12 humate Phosphate fertilizer eomposed of different powdered coal^* and rock phosphate.The result obtained showed that most of the extractable phosphorus of the samples was of negative value, while the lowest value was only equal to 14% of the P₂O₅ of powdered rock phosphate.The change of the negative value of the extractable phosphorus significantly correlated with the content of calcium and magnesium in powedered coal. The result also showed that the mechanism of the negative value is mainly due to the secondary retention induced by the calcium and magnesium ions of the powdered coal. Based on the results mentioned above, the phenomenon of negative value can be eliminated by using potassium sulfate or sodium fluoride to control the activities of Ca and Mg ions in the extraction system. In this paper a mixed extractant composed of 2% of citric acid-2% of sodium fluoride-7% of potassium sulfate which can control the activities of calcium, magnesium, iron and aluminium is proposed for the extraction of available phosphate from humate-phosphates. Pot experiment with rice and millet showed that the mixed extractant can basically eliminate the negative value of extractable phosphorus from samples, and the quantity extracted by the mixed extractant is well correlated with absorbed phosphorus by plants from the humate-phosphates as compared with the extraction of 2% citric acid. It is proved that the mixed extractant may be more practical for extraction of available phosphorus from humate-phosphates.