The E/Z-Photoisomerization of Schiff bases N,N'-bis(4-dimethylamino benzylidene)1,2-diaminoethane (BDAE) and N,N'-bis(4-dimethylaminobenzyli-dene)1,3-diaminopropane (BDAP) were studied by UV-Vis absorption spectroscopy and theoretical chemistry calculations. Photochemical investigations in solution depict the time resolved spectral changes, recorded before and after irradiation. The shift indicates the transformation from E to Z configuration of the C=N bond in solution for BDAE and BDAP. Spectra profiles and kinetic constants were evaluated using multivariate curve resolution and non-linear least squares curve fitting by toolbox of MATLAB program using the corresponding absorption spectra-time data. The experimental results show that BDAP can perform the photochromism easier than BDAE, may be due to the molecular topology difference.