Abstract: To advance the research, development, and application of research reactors and next-generation reactor technologies in China, ensuring nuclear facility safety is imperative for fostering the high-quality development of nuclear energy. During nuclear accidents, ensuring nuclear energy safety is paramount, with effective filtration of reactor containment gas emissions serving as a critical safeguard. Under nuclear reactor accident conditions, core materials may experience phenomena including cladding failure and steam explosions at the pressure vessel base. Fission products may infiltrate containment structures through cracks and steam pathways. The containment may accumulate substantial quantities of radionuclides including ¹²⁵I, ¹²⁹I, and ¹³¹I. Unmitigated release of these nuclides could pose severe environmental risks. Due to the complexity of the types of iodine in the emitted gas, it mainly exists in three forms: elemental iodine, aerosol iodine and organic iodine, and targeted treatment strategies must be taken. The performance of hydrophobically modified silver-loaded molecular sieves in removing methyl iodide (CH₃I) under extreme conditions (high temperature, humidity, and irradiation) was experimentally investigated in this study. AgX zeolites with controlled silver loadings (15%, 25%, 35%) were synthesized. Three silane coupling agents, such as octyltrimethoxysilane, phenyltriethoxysilane, and methyltrimethoxysilane, were employed for hydrophobic modification of AgX zeolites. This produced a series of materials with tailored silver contents and hydrophobicity gradients. The modified materials were characterized through FTIR, thermogravimetric analysis (TGA), and contact angle measurements to assess structural modifications. Adsorption performance for CH₃I in simulated accident gases was quantified using a custom gas adsorption system under controlled conditions (127 ℃, (330±5) kPa). The results demonstrate that all three silane agents effectively enhance zeolite hydrophobicity. Octyltrimethoxysilane-modified zeolites exhibite superior hydrophobicity, achieving contact angles exceeding 120°. The contact angle of the phenyltriethoxysilane- and methyltrimethoxysilane-modified molecular sieves also reache about 100°. All hydrophobically modified sieves show significantly higher CH₃I removal efficiencies compared to unmodified counterparts. The 25% Ag-loaded zeolite modified with 12% phenyltriethoxysilane demonstrates peak performance with 99% CH₃I removal. The molecular sieves modified with octyltrimethoxysilane still show good irradiation resistance at an irradiation dose of 4.2×10⁵ Gy, with the contact angle decreasing from 124° to 115° and the specific gravity of organic groups decreasing by 2% after irradiation. The removal rate of methyl iodide by the irradiated molecule is still higher than that of the unmodified molecular sieve, and the removal rate is about 60%. This work establishes optimized hydrophobic AgX molecular sieves as prime candidates for radioactive iodine filtration, offering novel design principles for adsorbents in nuclear containment venting systems.