In this paper, in addition to some elementary facts about the ultra-GROUPS, which their structure based on the properties of the transversal of a subgroup of a group, we focus on the relation between a group and an ultra-group. It is verified that every group is an ultra-group, but the converse is not true generally. We present the conditions under which, for every normal subultra-group of an ultra-group over a group, there exists a normal subgroup of that certain group. Moreover, by proving this feature that a monomorphism in GROUPS preserve the ultra-GROUPS over GROUPS, we show that, corresponding to any monomorphism in GROUPS, there is an ultragroup homomorphism on the subGROUPS of those GROUPS. Finally, we prove isomorphism theorems for ultra-GROUPS. These theorems connect three notions subultra-group, normal subultra-group, quotient ultra-group, and directly, similar to the isomorphism theorems in group theory and module theory are proved.