The effects of long-term fertilization on organic phosphorus fractions and availability in Shajiang black soil were studied with the method of the Bowman-Cole. The results of long-term located experiment showed that compared with the treatments of control, fallow and single applying chemical fertilizers, the combined application of organic manures and chemical fertilizers could increase the content of organic P significantly. The accumulative effects of different organic manures on organic P followed the order of cow dung＞pig dung＞wheat straw. Long-term fertilization mainly increased the content of moderately labile organic P. Correlation analyses showed that labile organic P was the direct resource of available P, moderately labile P was the supplement of labile organic P, the availability of moderately stable organic P and highly stable organic P was lower.