It is assumed that the weak interaction Hamiltonian for hyheroas decaying into a mu-cleon and a meson is of the Yukawa type, and that the parity violating factors of the terms involving Λ and Σ hyperons are respectively 1 +εγ5 and 1-εγ5 (ε=±1). The influence of strong interaction is taken into account for the innitial hyheron systems. It is found that the theoretical up-down asymmetries for various hyheron-decays are consistent with the experimental results. The prohabilities of the core of the hyperons being in various bare hyperon states are also estimated.