To ensure the safe design of hydrogen gas components, it is crucial to assess the hydrogen compatibility of various metallic materials through fatigue testing in high-pressure hydrogen gas. However, due to the high costs of such testing, only a few institutions can evaluate material performance under these conditions. As relying solely on high-pressure hydrogen testing is impractical, a low-cost and practical method is needed. The authors have developed a Continuous Chemical/Cathodic Hydrogen Charging test, which offers an affordable and effective alternative. This method involves continuously circulating a chemical solution through a pipe-shaped specimen to charge hydrogen during fatigue testing. Two charging methods are used: chemical charging, where hydrogen is produced through a reaction with ammonium thiocyanate, and cathodic charging, which involves electrolyzation inside the specimen. This study applied the technique to assess the hydrogen-induced fatigue crack growth in two types of Cr-Mo steels with different strengths (HV260 and HV359). The results showed that for the lower-strength steel, hydrogen’s effect on fatigue crack growth exhibited the upper bound, while for the higher-strength steel, the effect increased continuously as test frequency decreased. These findings align with results from high-pressure hydrogen gas testing.