The preparation of high-performance H2/CO2 polymer separation membranes is an urgent need to reduce the global greenhouse effect. Here, polyamide (PA) membranes with excellent H2/CO2 separation performance are produced using a facile interfacial polymerization (IP) plus heat treatment approach. The synergistic effect of the substrate-confinement and the control of the d-spacing and crosslinking degree of PA membranes creates sufficient H2 selective channels. The effects of test parameters such as feed temperature and feed pressure on membrane performance were investigated. The ultra-high H2/CO2 selectivity of 110 with excellent H2 permeance of 180 GPU is observed at 150 °C and feed pressure of 2 bar. In addition, PA membranes have high-pressure resistance (16 bar), high-temperature resistance (300 °C), and attractive durability (210 h). The excellent performance and facile preparation process make them expected to be one of the most promising membranes for H2/CO2 separation.