The investigation of the widespread 0D fluid model Ref. 1 - Ref. 8 for calculation of ion charge-state distributions (CSD) in electron cyclotron resonance (ECR) ion source Ref. 1 is presented. The modification of this model that allows one to describe the confinement and accumulation processes of highly charged ions in ECR plasma for gas mixing case more precisely is discussed. The description of the calculation technique for the time confinement of ions and electrons based on the theory of Pastukhov is also given, videlicet - calculation of confinement times during two stage minimization scheme of special functionals. The results obtained by this approach have been compared with available experimental data.