Abstract: According to the polymerization principle of free-radical aqueous solution, this paper synthesized the phosphine containing polymer retardant OPR-1 from three kinds of monomers, i.e., 2-acrylamide-2 methyl propane sulfonate (AMPS), styrene sulfonic sodium (SSS) and 3-dimethylaminoallyl phosphonic acid (DMAAPA). Then, its influences on slurry’s retardation performance and early compression strength were investigated by conducting orthogonal experiments. Accordingly the optimal synthesis conditions were determined, including the mass ratio of monomers m_AMPS∶m_SSS∶m_DMAAPA is 4∶3∶3, the dosage of initiating agent is 0.3%, the reaction temperature is 50 ℃, the pH is 6-7, and the reaction duration is 4 h. Infrared spectrum test results show that from the perspective of molecular structure, the polymer OPR-1 is the expected target product. The thickening time of the slurry with different dosages of retardant OPR-1 was measured under different temperatures and pressures. It is indicated that retardant OPR-1 can resist higher temperature. Under 160 ℃ and 101 MPa, the thickening time can be extended to 334 min. The early compression strength of the set cement with different dosages of retardant OPR-1 was tested, and no super retardation occurred. By virtue of scanning electron microscope characterization, combined with existing theories of slurry retardation, the retardation mechanism of retardant OPR-1 was discussed. It is concluded that reason for the occurrence of retardation is that retardant OPR-1 and Ca²⁺ and Al³⁺ in the cement constitute a strong chelation structure which cannot be damaged easily under high temperature, so complex “crystal nucleus poisoning” action is formed to hinder the growth and development of crystal nucleus