In order to improve the efficient resource utilization of phosphogypsum in paper-based gypsum board, the effect of soluble phosphorus, naphthalene water reducer (FDN) and modified starch (MS) on the performance of plasterboard were studied by X-ray diffraction, microcalorimetry and scanning electron microscopy. The results show that in the presence of FDN, soluble phosphorus will aggravate the retarding effect on hemihydrate gypsum and slightly reduce the adverse effect on the strength of gypsum samples. MS significantly shortens the hydration process of gypsum and reduces the strength of gypsum samples. Under the coexistence of MS and FDN, with the increase of soluble phosphorus content, the time for gypsum to reach the highest exothermic peak is prolonged, the peak value of hydration heat release and the total amount of hydration heat release in 2 h are decreased. 0. 50% (mass fraction, same below) soluble phosphorus can offset part of the promoting effect of MS on gypsum, and greatly reduce the strength of gypsum samples. In the presence of FDN, soluble phosphorus significantly reduces the aspect ratio of hydration products, the crystal morphology is irregular short column or block, and the crystal contact points are less. When FDN and soluble phosphorus coexist, MS causes the hydration products to appear small blocks and coarse plates. Under the dosage of 0. 4% FDN and 0. 2% MS, over 0. 50% soluble phosphorus will have a more adverse effect on the paper-based gypsum board. In this research, in order to ensure the paper core bonding performance of grade I, the soluble phosphorus content should not exceed 0. 25% .