Methods of mixed fields are extended to the case of hyperons. In order to take into account a new particle (Y-particle) which decays into a Λ-particle and a π-meson, a set of the so-called strong interactions between hyperson and mesons is assumed. Then the Λ-particle self-energy is calculated to the second-order terms through the use of the method of the present field theory. Some relations in which the masses of these hypersons and mesons are included are derived from the cancellation of its divergence. It is shown that their masses estimated in terms of the relations are as follows: Y∼2 600 me, Λ∼2 200 me, and the masses of scalar mesons which decay into two π-mesons are 800 me – 1 500 me. The model presented here gives results being in qualitative agreement with experiment.