[en] This presentation contains two subjects on the hadron spin polarization. The first is on the interaction to provide the spin asymmetry. The origin producing spin polarization of hadrons in high energy hadron collisions had been interpreted as a spin-orbit type interaction. However after one theoretical work which pointed out failure of the spin-orbit interaction not providing correct P_T dependence of the spin polarizations, its genuine origin becomes obscure. Here we clearly indicate what sort of spin-orbit interaction we should argue and we solve the existing confusion. The second subject is on the spin transfer mechanism in Λ production reactions. We attempt to resolve an anomaly found in the spin observables; presumably zero analyzing power A_N and spin depolarization D_NN of Λ hyperon production reactions from the quark parton recombination model, whereas apparently non zero in the observation. (author)