The crystal structures and thermodynamic properties of NDA-DMAC and NDA-NMP adduct crystals, the solubilities of 2,6-naphthalenedicarboxylic acid (NDA) in N,N-dimethyl acetamide (DMAC) and N-methyl pyrrolidone (NMP) over a temperature range from (293.2 to 373.2) K were studied in this paper. The results show that: (1) The asymmetric units of NDA-DMAC and NDA-NMP adduct crystals both contain one half molecule of NDA and one molecule of the solvent which are linked mainly by hydrogen bonds. (2) The thermal stabilities of the two adducts are both poor, and the initial dissociation temperature of NDA-DMAC and NDA-NMP adducts are about 306.29 K and 322.75 K, respectively. (3) The solubilities of NDA in DMAC and NMP solvents at (293.2 to 373.2) K both increase with the rise of experimental temperature. Below the dissociation temperature, the equilibrium solid phase is the, adduct crystal with the adduct solvent. Otherwise, the equilibrium solid phase is the pure NDA solid with the adduct crystal dissociating. The solubility data are correlated by the Buchowski equation or the nonrandom two-liquid (NRTL) activity coefficient model.