Aspergillus niger van Tieghem. is an industrially important soil-borne fungus. In biotechnological industries, it has been used for the production of many enzymes. It is well-known that the production of enzymes and its activity depends on co-factors. Some micro-elements act as cofactor of some enzymes involved in the production and function of industrially important enzymes or proteins in different ways. The micro-elements may also act on gene expression, protein folding and maintaining the activity of enzymes or proteins. In this study, Zn²⁺, Mg²⁺, Mn²⁺ and Fe²⁺ were used for the study of the effect of these micro-elements on the growth and the production of total soluble proteins of Aspergillus niger. This experiment suggests that few of Zn²⁺, Mg²⁺ and Mn²⁺ have important role in promoting growth and high production of total soluble proteins. Fe²⁺ has inhibitory effect on the growth as well as total protein production.