The influence mechanism of Al substitution on the nanostructure and properties of the calcium aluminosilicate hydrate（C-A-S-H） gel was investigated through the combination of experiment and molecular dynamics simulation. The results show that influence of Al on the molecular chain length of the aluminosilicate chain substitution of C-A-S-H gel structure can be considered to be due to the same molar amount of Si， but Al substitution leads to a larger increase in the basal spacing of C-A-S-H gel. Elevated curing temperature promotes the polymerization of the aluminate/silicate tetrahedra in the C-A-S-H gel， resulting in increasing mean chain length of C-A-S-H gel. When the curing temperature reaches up to 80 ℃， the spacing between the C-A-S-H gel primary layers abruptly reduces. Cross-linked structure are formed between the aluminosilicate chains on the adjacent main layer， which indicates parts of C-A-S-H gel are cross-linked. The mechanical properties of cross-linked C-A-S-H gel induced by the aluminum are greatly increased. Substituted Al bridges the broken silicon-oxygen chain. The formation of the long aluminosilicate chain improves the mechanical properties of C-A-S-H gel along the y-axis， but shows negligible effect on its mechanical properties along the x- and z-directions.