Water is one of the most important factors on the stability of tailings pond. The flood calculation and seepage calculation on the Yuntianhua phosphogypsum tailings pond are carried out under flood conditions, then the results are used for the stability calculation. In the calculation, considering the particularity of the phosphogypsum tailings pond, a revised scheme which combines the flood calculation and seepage calculation together is put forward. The results indicate that the tailings pond runs safely when the seepage-proofing and drainage facilities operate normally, but when the drainage facilities become invalid, the tailing pond is unsafe. The monitoring and maintenance of the drainage facilities should be strengthened in the actual operation.