In the spectral optical coherence tomography(OCT) system, a high depth of field can be achieved at the expense of the poorer transverse resolution. Interferometric synthetic aperture microscopy (ISAM) is an optical computed-imaging technique, which can make transverse resolutions at the different depths identical by resampling the spectrum data. The procedure of ISAM and the principle of error were analyzed and a reconstruction model of multi-scatterers is established. The multiple scatterers simulation is implemented by use of ISAM compared with the standard OCT methods. The approximate wavenumber domain algorithm is applied in ISAM, which can save much rebuilding time without the Stolt interpolation and the spectral OCT experiment system was developed. The experimental results showed that it can greatly reduce computational complexity to enhance the performance of real-time, which costs 50 s to finish one 320 pixel×265 pixel image.