MCM-48 microspheres have been repeatedly synthesized in cetyltrimethylammonium bromide-tetraethylorthosilicate-ammonia solution-water media with a fixed alcohol-to-water molar ratio of 0.15 by increasing the amounts of water and ethanol simultaneously. The cubic ordered pore arrangement is proved by the XRD and TEM measurements. Experiments show that the sole increase in either the ethanol or water addition would result in the formation of MCM-41 mesophase. The results indicate that the alcohol-to-water molar ratio is an important factor for controlling the formation of MCM-48 microspheres. The mechanism is primarily discussed.