By analysing the carbon isotope in the phosphatic series section in Weng’an, this paper studies the phosphorite-forming events, biological events and changes of the ancient ocean evolution in the Sinian Doushantuo period. The δ13Ccarb value’s positive excursion, deposition of phosphorite and biological events had some relevance. The oceanic anoxic events cause: the bottom water to be rich in phosphorus. With the improvement of the ancient ocean circulation, the bottom water with rich phosphorus is migrated to the shallow water by the upwelling current and deposited into the phosphate, which can supply nutrients for the biosphere.