A series of experiments were carried out in linked vessels with two spherical vessels of 600 mm and 350 mm diameter respectively and pipe of 60 mm diameter to investigate the influential factors on H-2-air mixtures explosion. This research is focused on the effects of ignition position, initial pressure and pipe length on H-2-air mixtures explosion in linked vessels. The experimental results show that the different ignition position has less impact on the maximum hydrogen explosion pressure in big vessel, however, the impact on the maximum hydrogen explosion pressure in small vessel and the maximum hydrogen explosion pressure rising rate in linked vessels is obvious. The initial pressure has a distinct effect on the maximum hydrogen explosion pressure in linked vessels. In big vessel, the maximum hydrogen explosion pressure increases with the increasing of initial pressure nearly linear relationship. In small vessel, the maximum hydrogen explosion pressure also increases with the increasing of initial pressure. Moreover, the maximum hydrogen explosion pressure has a sharp increase from 0.02 MPa to 0.03 MPa. When the ignition in big vessel, the maximum hydrogen explosion pressures are all increased with the pipe length. Meanwhile, the change of the maximum hydrogen explosion pressure in small vessel is more severe than in big vessel. The maximum hydrogen explosion pressure in the big vessel increases with pipe length when the ignition is located in the small vessel. However, the maximum hydrogen explosion pressure in small vessel increases first then decreases. The maximum hydrogen explosion pressure, the maximum rates of pressure rise and the time delay between ignition in the big and small vessel are discussed. (C) 2017 Elsevier Ltd. All rights reserved.