Using tetraethyl orthosilicate as a silica source and cetyltrimethylammonium bromide as a template, MCM-48 mesoporous molecular sieves were synthesized with hydrothermal methods. Reducing the pH of the solution during synthesis improved the yield of MCM-48 and enhanced its stability. While the pH was adjusted to 5, a high yield of 98% was gained. XRD and N-2 adsorption-desorption isotherms were used to characterize the synthesized samples. These mesoporous molecular sieves showed high specific surface areas and ordered channel systems.