The behavior of hydrogen-induced hardening of 310S and 304 austenitic stainless steels was investigated by using nanoindentation constant strain rate (CSR) and strain rate jump tests. Hydrogen increases the hardness at all strain rates, and the effect of hydrogen-induced hardening becomes stronger with increasing the strain rate in 310S steel. Additionally, hydrogen increases the strain rate sensitivity in 310S steel, and enhances pile-up around indentation with decreasing the strain rate. The interaction between hydrogen and mobile dislocation is responsible for the dependence of hydrogen-induced hardening on the strain rate. Hydrogen can keep pace with mobile dislocation and enhance the movement of mobile dislocation at a small strain rate (0.005 s(-1)), while hydrogen lags behind mobile dislocation and inhibits the movement of mobile dislocation at a large strain rate (0.5 s(-1)). Since hydrogen suppresses the alpha'-martensite transformation, hydrogen-induced hardening of 304 becomes weaker than that of 310S. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.