The effect of added monovalent electrolytes on the myelin formation of cardiolipin is investigated by optical microscopy observations. The results show that the myelin formation strongly depends on the concentration rather than the type of electrolytes. Myelin figures are observed only in a certain concentration range of electrolytes, and the diameter of the myelin figures decreases with increasing of the electrolyte concentration. Furthermore, the theoretical model of myelin formation for the neutral lipids developed by Huang-Zou-Witten [J.R. Huang, L.N. Zou, T.A. Witten, Eur. Phys. J. E. 18 (2005) 279-285] is extended to the charged membrane system by taking into account the electrostatic interaction to understand the mechanism of myelin formation. The theoretical results well produce our experimental results. (C) 2010 Elsevier Inc. All rights reserved.