The TS-1 particles grown on carbon nanotubes decorated nickel foam (denoted as MTS-1S) are successfully synthesized by a steam-assisted crystallization method that does not waste the gels and is more convenient, economical, and efficient than the traditional hydrothermal method. MTS-1S possesses a hierarchical porous structure of micropores, mesopores, and macropores and a high content of titanium in the skeleton, which is beneficial for the diffusion of reactants and products and exhibits excellent catalytic performance for the epoxidation of propylene. The impact of water on the formation of acid sites has been demonstrated by density functional theory (DFT). The acid sites of MTS-1S can be tuned by controlling the amount of water at the bottom of autoclave during steam-assisted crystallization, which significantly increases the selectivity to propylene oxide. Finally, the impact of acid sites of Si- OH and Ti-OH groups (Ti located in a defect structure, adjacent to Si-OH) on the byreaction of epoxidation of propylene is confirmed by simulation.