During solid-state polycondensation of crystaHine nylon 66 salt(Hexamethylenediam-monium adipate) the mechanism of reaction，crystalline morphologies and the relations of thermal behaviour to the thermal history for the nasent nylon 66 have been studied by the use of a number of techniques including determination of conversion rate and of intrinsic viscosities，IR，polarized light microscopy，SEM and DSC．The results indicate that the de-fects in crystals of nylon 66 salt may introduce the nucleation of the reasulting polymer phase

and there are epitaxial crystallization processes in the polycondesation．It was found that the morphologies of fibril-like structure are formed in nascent nyIon 66．and the orien-tation of fibrils is dependent on the conditions used．Double melting peaks duHng DSC ana-lvsis for the nascent nylon 66 in this system are discussed．