Phosphogypsum (PG) is a by-product of phosphor acid producing, which has become the primary barrier for the development of phosphate fertilizer industry. This paper proposes a series of technical process for the decomposition of PG with Fe addition. The FactSage 7.0 was used as feasibility analysis. Results from the TGA revealed that the initial decomposing temperature of PG was 590 degrees C, lower 300 degrees C than without FeCl3 immersion. The decompositions of PG and lignite in multi-atmosphere were performed at different molar ratio in the tube furnace, when the molar ratio of lignite and PG was 1.2:1, the purity of CaO in solid products could reach 90.6%. Fluidized bed experiments were done in a vertical tube furnace, results indicated that after a multi-atmospheres cycles experiment, target production CaO purity could achieve 93.8%. The present research proves that PG with Fe addition decomposed in fluidized bed under multi-atmospheres is feasible.