Hierarchical porous materials have a potential for sensitive and fast gas detection due to their large specific surface area (SSA) and good gas diffusion. Herein, a facile optochemical sensor capable of generating visually detectable gaseous hydrogen chloride (HCl) was reported. The sensor used 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPPH2) as an optical probe, and the optical probe was immobilized in the hierarchical porous silica nanofiber membrane which was fabricated by the electrospinning method. The presence of mesopores and macropores promoted the gas adsorption and diffusion of the TCPPH, functionalized hierarchical porous silica nanofiber membrane (TCPPH2-SiO2 HPNFM). As a consequence, the TCPPH2-SiO2 HPNFM sensor exhibited a highly sensitive and time-efficient response for HCl gas detection. The results indicated a detection limit of 17 ppb and a response time of 5 s. A pseudo-secondorder rate constant of 8.55 X 10(-5) was observed because of the mesopores, which generated a large SSA and high pore volume. The sensor also had a vivid color variation from cameo to green and a good reversibility, which had a promising alternative to develop a low-cost HCl gas-sensing system.