The double melting behavior of a thermotropic liquid crystalline polyimide was studied by means of differential scanning calorimetry (DSC), polarized light microscopy (PLM), transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). This liquid crystalline polyimide exhibited a normal melting peak around 278 degreesC and transformed into a smectic A phase. The smectic A phase changed to nematic phase upon heating to 298 degreesC, then became isotropic melt around 345 degreesC. The samples annealed or isothermally crystallized at lower temperature showed double melting endotherms during heating scan. The annealing-induced melting endotherm was highly dependent on annealing conditions, whereas the normal melting endotherm was almost not influenced by annealing when the annealing temperature was low. Various possibilities for the lower melting endotherm are discussed. The equilibrium melting points of both melting peaks were extrapolated to be 283.2 degreesC. Combined analytical results showed that the double melting peaks were from the melting of the two types of crystallites generated from two crystallization processes: a slow and a fast one. Fast crystallization may start from the well-aligned liquid crystal domains, whereas the slow one may be from the fringed or amorphous regions.