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The effect of hydrogen concentration on the ultrasonic surface wave propagation properties in the 304 stainless steel has been investigated experimentally in this paper. The cathodic hydrogen charging has been used in experiment. The properties of ultrasonic surface wave and the mechanical property changes have been tested. The experimental results show that the ultrasonic attenuation coefficient is increased clearly in the cathodic hydrogen charging duration, meanwhile the ultrasonic velocity is decreased in the same time. With the charging in progress, the attenuation coefficient and the velocity are tend to a constant value, which is indicated that the hydrogen in the surface of specimen becomes saturated. It is found that the microhardness of material after hydrogen charging is decreased remarkably.