Abstract: The role of surfactant CTMABr in the synthetic gel system at the process of synthesis of mesoporous material MCM-41 molecular sieve has been studied by ¹H, ¹⁴N, ¹³C NMR techniques. A Local Concentrated Effect （LCE） of surfactant is discovered. And a possible formation mechanism of mosoporous molecular sieve MCM-41 with the role of surfactant in the syntheticg el is also proposed, which is via the condendation and self-assembly of silicon surfactan tmicelles. Under the actual synthesis conditions to form a silicatropic mesophase followed by silica crosslinking, then sllicate species condensed to generate local concentration phenomnon. This kind of LCE might cause the formation of a liquid-crystal mesostructure （hexagonal, lamellar,or cubic）, the nature of which depends on the composition of the mixture, the pH, the temperature, and the reaction time. Polycondensation of the silicate spedes lead to the formation of a rigid structure.