Molecule chains of spider silk protein readily self-assemble into ordered structure such as beta-sheets when a filament is pulled away from dilute aqueous solution of spider major ampullate silk protein. There is no need to change the pH, the temperature, or the ionic strength of the solution to aid filament formation. Circular dichroism spectroscopy confirmed that the silk protein in such aqueous solution was initially in random coil formation but with time would transform to beta-sheets; the process was temperature-dependent. Amino acid analysis showed that reassembled (regenerated) and native spider silks were similar in composition. The morphology and structure of the reassembled silk were investigated by scanning electron microscopy and Raman spectroscopy. The mechanical properties of the reassembled silk were studied in some detail. Our study indicates that reconstituted spider silk self-assembles into respectable filaments. However, it is clear that the spinning process is crucial for the desirable material properties of native silks.