An easy and reproducitble synthesis procedure to obtain a cubic mesoporous molecular sieve MCM-48 has been investigated by the hydrothermal reaction between sodium silicate and hexadecyltrimethylammonium bromide in the presence of auxiliary additives such as ethanol, methanol, etc. The resultant MCM-48 exhibits not only an excellent structural order but also a single crystal-like morphology of cubes truncated by rhomb dodecahedron. The MCM-48 cubic crystals grow from disordered particles that are formed during the initial period of the hydrothermal reaction, subsequently transforming to a lamellar phase, This kinetic-controlled crystallization process for the MCM-48 is very similar to that of microporous zeolites, the activation energy being 14 ㎉ mol＾1.