On the basis of previous researches and engineering practice，total 52 cubic and 33 prismatic phosphogypsum specimens were made by a water/cement ratio of 0.43, where nine mix proportions for phosphogypsum were involved according to the different mixture of phosphorous slag micro-powder, hydrated lime, cement, water reducer and retarder. Furthermore, total 8 one-second scale wall models using the 7th mix proportion were also made for axial compression tests.Experimental results combined with the earlier research show that the compressive strength of cast-in-situ phosphogypsum wall is about 0.68 times the prism compressive strength, while the latter is about 0.8 times cube compressive strength. Additionally, the recommended value of material weight is around 14.0 kN/m3 to 15.0 kN/m3. Based on the reliability analysis of engineering examples, the material partial coefficient of cast-in-situ phosphogypsum is recommended as 1.9, and the standard value and design value of phosphogypsum compressive strength are given according to the mix proportion examined in this paper.