Solubilities, densities, and refractive indices of the two ternary systems (LiBO2 + NaBO2 + H2O) and (LiBO2 + KBO2 + H2O) at 298.15 K and 0.1 MPa were conducted with the method of isothermal solution saturation. The diagrams of solubilities, densities, and refractive indices were constructed using experimental data. They both contained one invariant point co-saturated with two salts, two biphasic regions, and one triphasic region. As the concentration of sodium metaborate (potassium metaborate) increases in solution, the density and refractive index change regularly and reach a maximum value at the invariant point. The densities and refractive indices change regularly with the sodium metaborate (potassium metaborate) concentration increasing in solution and reach the maximum value at the invariant point.