To solve the problem of cement slurry suspension instability caused by a geothermal gradient in low-pressure and leakage formation, a hydrophobically associating long-chain polymer (PSAN) was designed as a suspension stabilizer by introducing hydrophilic monomer acrylamide (AM), temperature-resistant monomer 2-acrylamide-2-methyl propane sulfonic acid (AMPS), hydrophobic monomer styrene (St) and temperature-sensitive monomer N-vinyl caprolactam (NVCL). The synthesis conditions of PSAN were optimized by orthogonal response surface method. The structure and performance of PSAN were characterized and tested by IR, ¹H-NMR, GPC, SEM, TG, high-temperature rheology, and fluorescent probes. The research and analysis showed that PSAN had a good temperature response. At 30~65 ℃, the apparent viscosity of PSAN aqueous solution increased with the increase of temperature. At 65 ℃, the hydrophobically associating ability of PSAN was enhanced, and the retention rate of the apparent viscosity of its aqueous solution at 65~110 ℃ was still more than 83%. The good temperature response of PSAN was conducive to the suspension stability of cement slurry under the condition of large temperature differences. When 1% bwoc (percentage of cement mass) was added to the cement slurry, the free liquid of the cement slurry was 0, the water loss was less than 90 mL, and the density difference between the upper and lower sections of the cement stone column was less than 0.01 g/cm³. SEM analysis showed that there was a network structure formed by hydrophobic association between PSAN molecules in cement. In a word, under the condition of 30~110℃ (80℃ large temperature difference), the suspension stabilizer PSAN can effectively alleviate the floating of light materials and the sinking of heavy materials in cementing slurry through the hydrophobic association between molecules, and ensure the suspension stability of cementing slurry, thus contributing to the safety of cementing construction and improving the quality of cementing.