In this paper, an MCM-41 single crystal with hexagonal circular bicone form has been observed, and the special morphology of the single crystal appears to be a combination of circular bicone and hexagonal prism forms. As far as we know, the circular bicone faces have not been reported in crystal morphologies before. The results show that the morphology of MCM-41 single crystals remains essentially the same and can grow larger via the multiple-growth method in extremely dilute ammonia solution. Moreover, the morphology of the MCM-41 crystals can be effectively modulated by adding inorganic salts (KCl, NaCl) to the synthetic system. Increasing the concentration of the salts (KCl, NaCl) in the solution can make the aspect ratio and the conical angle vary consistently. A novel crystal form of hexagonal circular bicone of an MCM-41 single crystal has been observed for the first time. The special morphology of the single crystal appears to be a combination of circular bicone and hexagonal prism forms. The morphology of an MCM-41 crystal can be controllably modulated through the addition of inorganic salts in the synthetic system. [ABSTRACT FROM AUTHOR]