Abstract: Astudy has been made of the binary salts systems Li₂SO₄-MgSO₄ and LiNO₃-Mg(NO₃)₂ by the visual polythermal and DTA methods. An incon-gruently melting compound Li₂SO₄·2MgSO₄ occurring at 832℃ was found in the Li₂SO₄-MgSO₄ system. The eutectic point between Li₃SO₄ and Li₂SO₄·2MgSO₄ occurring at 647℃ lies in the composition of 23.6 Wt% MgSO₄. The values of eutectoid are 4.2% MgSO₄ and at 552℃. The system LiNO₃-Mg(NO₃)₂ is of a simple eutectic type, the eutectic point occurring at 200℃ contains 47.3% Mg(NO₃)₂. No solid solution existed on the both sides of LiNO₃ and Mg(NO₃)₂.