The paper presents a study of three semi-empirical laws of melting. The study utilises the Improved Unsymmetrized Self-Consistent Field Method (IUSCFM) for strongly anharmonic crystals with complex lattice and the energy criterion in calculating the melting curves of some alkali-halides. The energy criterion was proven correct along the melting curves particularly in the case of CsCl type of structure. The calculations of the melting curves for crystals of nine alkali-halides (KCl, KBr, KI, RbCl, RbBr, Rbl, CsCl, CsBr, Csl) are presented. The thermodynamic properties of these salts along the curves are also determined. A comparison of the calculated results and the experimental data is included.