The electronic and tautomeric structures of some novel pyrazolyl quinolinone derivatives are investigated using DFT/B3LYP/6-311++G (d, p) level of theory. The results of MO calculations show that all the studied compounds 1- 6 are planar, as indicated from the calculated dihedral angles. The calculated EHOMO and ELUMO energies of the studied compounds can be used to describe the extent of charge transfer in the studied molecules and to calculate the global properties; the chemical hardness (η), global softness (S), electrophilicity (ω), and electronegativity (χ). The effect of substituents of different strengths on the geometry, energetic and nonlinear optical properties are analyzed and discussed. The choice of these substituent's in the studied compounds aims at creating a push-pull system on pyrazolyl quinolinone structure which pave the way to understand their nonlinear optical properties. The calculated nonlinear optical parameters (NLO); polarizibilty (α), anisotropy of the polarizibility (Δα) and first order hyperpolarizibility (β) of the studied compounds have been calculated at the same level of theory and compared with the proto type Para-Nitro-Aniline (PNA), show promising optical properties. 3D- plots of the molecular electrostatic potential (MEP) for some of the studied compounds are investigated and analyzed showing the distribution of electronic charge density of orbitals . describing the electrophilic and nucleophilic sites of the selected molecules.