A general expression of the Curie temperature (T-c) and spontaneous polarization (P-s) of lithium niobate (LN) crystals is energetically proposed by employing the viewpoint of the bond energy of constituent chemical bonds within the LN crystallographic frame. The calculated T-c values of various pure and doped LN crystals are in a good agreement with those reported data. P-s values of these LN crystals can also be quantitatively estimated in this work. It is found that the Li site is a sensitive lattice position to dominate the ferroelectricity of LN crystals. This novel method provides us a good understanding of ferroelectric behaviors of LN crystals, which may be applicable to the estimation of ferroelectric behaviors of LN-type solids.