Abstract: In the paper, a new kind of electrochemical sensor was used for measuring the permeation rate of atomic hydrogen (H permeation current I) through the sensor in 5% HCI solution containing ferric ion with different concentrations. The susceptibility of brittle fracture and the fracture mechanism of UNS G10190 steel in the solution were studied by slow strain rate tensile technique (SSRT), scanning electron microscope (SEM) and cathodic and anodic polarization. The embrittlement of the steel in the solution was expressed as index of embrittlement (F%). The results showed that the fracture mechanism of the steel in 5%HCl aqueous solution containing ferric ion would be changed from hydrogen induced cracking (HIC) to anodic dissolution in nature with the increase of the concentration of ferric ion in the solution.