Abstract: The properties of dense matter are studied within the relativistic meanfield theory. The equation of state (EOS) of dense matter are constructed covering a wide range of temperature, proton fraction, and density for the use of supernova simulations. The relativistic meanfield theory is employed to describe the uniform matter, while the ThomasFermi approximation is adopted to describe the nonuniform matter. The EOS of neutron star matter is discussed with the inclusion of hyperons. It is found that the EOS at high density can be significantly softened by the inclusion of hyperons. The ¹S₀ superfluidity of Λ hyperons may exist in massive neutron stars.