In the present study, the influences of hydrogen on the mechanical properties as well as the pre-strain on the HE susceptibility of X100 pipeline steel were investigated by combining electrochemical hydrogen charging and tensile experiments. Both the yield and tensile strength decrease with the increasing hydrogen charging time no matter the values of pre-strain. When the charging time is 12 h, the yield strength and tensile strength was reduced by 3% and 9%, respectively. The longer the charging time, the stronger the HE damage of the steel. Besides, when the hydrogen charging time is same, HE sensitivity increases with the pre-strain values. When the charging time is 6 h, the HE sensitivity coefficient is 40.24% without pre-strain, and it increases to 49.26% with the pre-strain value increases to the 2%. The hydrogen effective diffusion coefficient reduces gradually with the increasing pre-strain values. The coefficient is 5.45 x 10(-7) cm(2)/s without pre-strain and it reduces to 1.21 x 10(-7) cm(2)/s with the pre-strain value increases to the 3%. When the hydrogen charging time is same, HE sensitivity increases with the pre-strain values. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.