The influences of solid-state reaction and sol-gel synthesis methods on the permeability through the La5.5W0.6Mo0.4O11.25-delta membranes were investigated firstly. Then the superior sol-gel route was selected to synthesize chlorine-doped La5.5W0.6Mo0.4O11.25-delta-x/2Clx (LWMClx, x = 0-0.20) series membranes. The effects of chlorine doping on hydrogen separation performance through LWMClx hydrogen permeable membranes were determined in detail. The developed LWMCl0.1 membrane exhibited higher hydrogen permeability and better stability compared to its parent one, achieving 0.15 mL min(-1) cm(-2) at 1000 degrees C in dry atmosphere (50% H-2 in He), confirming the benefits of chlorine doping strategy.