The effect of the phosphoric acid and phosphate rock quality on watersoluble P 2O 5 in granular TSP by slurry process is discussed. The measures for improving watersoluble P 2O 5 in product are also presented by controlling ratio of acid and rock, concentration of phosphoric acid(42%~52%P 2O 5), reactive temperature(90~100℃), size of phosphate rock(that of less than 0.074 mm is 80%~90%) and dry temperature(<100℃ for dried material at outlet).