We presents the study carried out by the technique Z-Scan, to analyse the nonlinear optical properties of (E)-4-(4-dimetylaminophenyl) but-3-en-2-one and (E)-4-(4-nitrophenyl) but-3-en-2-one, diluted in Ethyl Acetate with concentration levels of [0.02M, 0.08M, 0.23M] and [0.0047M, 0.013M, 0.041M] respectively. The measurements were performed using a Nd:YAG laser emitting at 532nm, for samples with Leff =1mm thickness, and a automated scanning of 10cm symmetric to the lens focus, the iris diameter was 1mm, the samples were also characterized by an UV-Vis Spectroscopy. We calculated the nonlinear refractive index (η2), the nonlinear absorption coefficient (β) and the the third-order nonlinear optical susceptibility (χ3) of the two researched compounds. The results show a combination of thermal response and nonlinear self-defocusing and self-focusing, which make their application interesting as new optoelectronic materials.