The linearized Eliashberg equations for a superconductive system in strong exchange fields have been investigated. An iteration procedure has been used for including the asymmetry of the gap function φ(ω) with respect to ±ω and an approximate solu-tion has been obtained in the lowest order of the iteration equation. The results show that the asymmetry in the gap function can considerably change the critical exchange field as a function of temperature in moderate or stronger electron-phonon coupling (λ≥ 0.5) systems.