The reaction gel mixtures of molar composition (0.3${sim}$2.1) $SiO_2:;(0.10{sim}0.50);CTABr:;0.15{sim}0.23);TMAOH:;(20{sim}100);H_2O$ we prepared and then aged at room temperature for a definite duration. The aged gel is reacted hydrothermally at $150^{circ}C$ for 2 days. The pH of reaction gel during synthesis is strongly influenced by the concentration of TMAOH and silica source. The pH change affects the phase of product, which is monitored by X-ray diffractometer. With increasing the TMAOH ratio from 0.19 to 0.23, the gel becomes more basic, and the product involves more lamellar phase. At TMAOH ratio lower than 0.19, the hexagonal phase is lower with decrease of pH. The content of the lamellar phase increases at a lower $SiO_2$ concentration, and higher concentrations have a clear detrimental effect on the crystallinity ofMCM-41 due to an excess silica source. The best quality MCM-41 is synthesized from a reaction gel composition of $1.0;SiO_2:;0.27;CTABr:;0.19;TMAOH:;40;H_2O$. The pH values of this gel, aged one for 24 hr, and reacted one at $150^{circ}C$ for 2 days are 12.3, 11.5, and 10.5, respectively. Gel aging for 24 h is essential for preparing high quality MCM-41. Longer aging causes a decrease of hexagonal phase.