Abstract: The behaviors of corrosion and galvanic nickel based alloy couple of sulfur-resistant casing P110SS in the high sulfide gas well annulus protection fluid were studied. This study was conducted in a high temperature/pressure reactor which simulated the operating environment of oil ring annulus in Puguang Gas Field well. In addition, P110SS sulfur-resistant casing overall performance such as collapse strength, pipe body yield strength and internal pressure strength was also analyzed. Without the presence of hyperbaric H₂S/CO₂, the annulus protection fluid protected the casing excellently and the galvanic accelerated couple corrosion on P110SS casing was not significant. Thus, the collapse strength, pipe body yield strength and internal pressure strength of P110SS casing were reduced slightly. However, in the hyperbaric environment of H₂S 5.0MPa, CO₂ 3.0MPa, the annulus protection fluid did not protect the casing properly and the corrosion rate was increased by around 100 times. Additionally, the galvanic accelerated couple corrosion on P110SS casing was significant. As a consequence, the performance of P110SS casing including the collapse strength, pipe body yield strength and internal pressure strength was decreased considerably.