Supported ionic liquid membranes (SILMs), owing to their capacities in harnessing physicochemical properties of ionic liquid for exceptional CO2 solubility, have emerged as a promising platform for CO2 extraction. Despite great achievements, existing SILMs suffer from poor structural and performance stability under high‐pressure or long‐term operations, significantly limiting their applications. Herein, a one‐step and in situ interfacial polymerization strategy is proposed to elaborate a thin, mechanically‐robust, and highly‐permeable polyamide armor on the SILMs to effectively protect ionic liquid within porous supports, allowing for intensifying the overall stability of SILMs without compromising CO2 separation performance. The armored SILMs have a profound increase of breakthrough pressure by 105% compared to conventional counterparts without armor, and display high and stable operating pressure exceeding that of most SILMs previously reported. It is further demonstrated that the armored SILMs exhibit ultrahigh ideal CO2/N2 selectivity of about 200 and excellent CO2 permeation of 78 barrers upon over 150 h operation, as opposed to the full failure of CO2 separation performance within 36 h using conventional SILMs. The design concept of armor provides a flexible and additional dimension in developing high‐performance and durable SILMs, pushing the practical application of ionic liquids in separation processes. A thin, mechanically‐robust, and highly‐permeable polyamide armor is designed and manufactured on the supported ionic liquid membranes (SILMs) via one‐step and in situ interfacial polymerization, fundamentally resolving poor structural and performance stability of the SILMs. The armored SILMs display high operating pressure exceeding most SILMs, and ultrahigh CO2/N2 selectivity of about 200 and excellent CO2 permeation even upon over 150 h operation.