Magnetization, magnetic susceptibility and X-ray thermal expansion of the Ho1-xYxCo3 system with metamagnetic Co sublattice were studied in wide temperature and concentration ranges. Due to a strong f-d exchange interaction, at low temperatures the Co sublattice is in a strongly magnetic state in the Ho rich compounds, which can be turned into a weakly magnetic state by Y substitution. Temperature induced metamagnetic transitions were observed in the Ho-rich compounds, both the magnetic sublattices still remained magnetic. The magnetic phase diagram of the Ho1-xYxCo3 system includes also spin-reorientation phase transitions occurring due to a competition between the anisotropies of the Ho and Co sublattices.