Abstract: The experiment system for stress corrosion crack growth rate measurements based on reversing direct current potential drop method and its principle were introduced. In the experiment system, the water chemistry board, controlling system, autoclaves, servo loading system and data acquisition system were described in detail. Commercial 301 stainless steels were used to validate the stability and reliability of the system in pure water at 320 °C and 15.5 MPa. Crack length vs. time curves were obtained, and the effects of dissolved gases and impurities additions on crack growth rate were evaluated. Scanning electron microscopy was used to analyze the fractography of the tested specimen. The results showed that the system can monitor the crack propagation with high stability and accuracy, and can yield useful key insights into crack growth in high temperature and high pressure water.