Hydrogenation of silicene has been shown to be an efficient way to open the band gap of silicene and manipulate its electronic properties for application in electronic devices. However, the reaction energy barrier of silicene hydrogenation is quite high, which prevents the occurrence of this chemical reaction. Using density functional theory calculations, we propose an alternative approach to reduce the energy barrier, thus facilitating hydrogenation of silicene. Our results demonstrate that biaxial strain and uniaxial tensile strains along armchair direction can reduce the energy barrier of H2 dissociative adsorption on silicene significantly, and the barrier decreases as the strains increase. However, the biaxial strain has better effect on the energy barrier reduction. It is found that the barrier reduces from 1.71 to 0.24 eV when the biaxial strain reaches the critical value of about 12%, above which the structure of silicene after hydrogenation would be destroyed. In this way, the reaction time for the hydrogenation of silicene can be reduced significantly from 8.06 × 10^16 to 1.68 × 10^-8 s. The mechanism of the effect of tensile strains can be understood through analysing density of states of the system and atomic charge transfer during hydrogenation.