Abstract: Coal spontaneous combustion poses a serious threat to coal mine safety, and chemical inhibitors are widely used as the primary means of control. However, conventional inhibitors applied in underground coal mines generally exhibit poor environmental compatibility, high cost, and low efficiency. Therefore, the development of a phosphorus-based inhibitor with high efficiency, low cost, and environmental friendliness is essential for improving its practical application in fire prevention. Modified zirconium phosphate (MZrP) is synthesized via an intercalation method using α−zirconium phosphate, iso-octylamine, and anhydrous ethanol as raw materials, and is employed as a high-efficiency inhibitor for coal spontaneous combustion. To evaluate the inhibitory performance of MZrP at different concentrations, temperature-programmed gas chromatography is conducted. The concentrations of indicator gases and the crossover temperature during the low-temperature oxidation of raw and treated coal samples are compared to analyze variations in inhibition rate at different concentrations. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) are conducted to characterize changes in coal surface morphology and active functional groups at the microscopic level. Thermogravimetric analysis (TGA) is performed to investigate the effects of MZrP on thermal mass loss and characteristic temperatures, thereby elucidating the inhibition mechanism. The results show that the concentrations of indicator gases released during the oxidation of treated coal samples are significantly lower than those of raw coal. With increasing MZrP concentration, gas release decreases, while the crossover temperature and inhibition rate increase. The inhibition rate of the coal sample treated with 5% MZrP reaches 62.85%. After intercalation, MZrP is uniformly distributed on the coal surface, forming a dense inhibitory layer that effectively isolates oxygen and exerts a physical inhibition effect. Compared with raw coal, the contents of methyl and methylene groups, as well as thermal mass loss, are significantly reduced in treated coal samples. The critical temperature of coal samples treated with 3% and 5% MZrP is increased by 2.2 ℃ and 2.81 ℃, respectively, while the temperature corresponding to the maximum mass loss rate is increased by 15.6 ℃ and 23.1 ℃, respectively. As the concentration of MZrP increases, more inhibitor reacts with active functional groups in coal, further increasing the critical temperature and the temperature of maximum mass loss rate, thereby achieving efficient chemical inhibition of coal spontaneous combustion.