Abstract: The model cascade plays a very important role in the study of cascades separating multicomponent isotope components. Three widely used model cascades, including the Q-cascade, the quasi-ideal cascade and the matched abundance ratio cascade, were investigated. Their backgrounds and significances, basic properties and applications were introductorily explained. Through comparing the analytical expressions of some key parameters and separation properties, it is shown that the three model cascades have significant similarities and intrinsic relationships. Matched abundance ratio cascade proves to be a special case of the quasi-ideal cascade. As a type of cascades of continuous profile, the Q-cascade has approximately constant partial cuts for each component, just like the case in the quasi-ideal cascade. Moreover, the same key parameter called molar mass of a virtual component M* determines the separation properties of both Q-cascade and quasi-ideal cascade, in a similar rule. Therefore, they can be treated as the same class of cascades.