In the present study, a novel series of 4-((E-2-benzylidenehydrazinyl)-1-ethylquinolin-2(1H)-one derivatives have been designed and synthesized from the reaction of 4-hydrazinoquinolin-2(1H)-one with 4-substituted benzaldehyde possessing electron donating and withdrawing groups. The structures of the obtained hydrazone compounds have been characterized in detail using IR, NMR, mass spectra and elemental analysis as well. The assigned chemical shifts of hydrazone compounds were compared with the NMR data. We observed that the presence of withdrawing group in hydrazonquinolinone showed a lower field than electron donating group. Also, the in vitro antitumor activity of all hydrazone compounds was investigated against human Hepatocellular carcinoma cell lines (HePG-2) using the colorimetric method and studying structure-activity relationship analysis (SARs). The electronic structures of some novel quinolinones derivatives are investigated using DFT/B3LYP/6-311++G (d, p) level of theory. In theoretical studies, the global chemical activity descriptors (FMOs, softness, hardness, electron affinity, ionization potential, etc.) and MEP were computed to predict important information related to the stability and reactivity of the prepared molecules. Compound 8 is the more stable product. To explain the nonlinear optical (NLO) properties of the synthesized compounds, the dipole moment, polarizability, and initial hyperpolarizability values (in the range 69 x 10-30 - 109 x 10-30 esu) have been calculated and compared with Para-Nitro-Aniline (PNA), as a reference material show promising optical properties. In addition, the 1H and 13C-NMR chemical shifts of the synthesized compounds were simulated by GIAO manner and compared with the experimental chemical shifts results.