Abstract: Four different mixtures of 10-3 mol/L Rhodamine B laser dye, 0.1 g PMMA and one of Fe3O4 nanoparticles weights (0.02, 0.04, 0.06 and 0.08 g) and other four mixtures for the Styryl 9M laser dye with the same contents had been prepared using chloroform solvent. Eight different thin films had been made from these mixtures using drop casting method. The absorption spectrums of these thin films had been taken. The absorption spectral properties as (peak wavelength, peak absorbance and frequency difference at half absorbance maximum) had been measured depending on the absorption spectrums for thin films. The non-linear optical properties as (Transmittance difference ΔΤρ-v), non-linear phase shift ΔΦ0, non-linear refractive index n2, Minimum normalized transmittance T(Z) and non-linear absorption coefficient β) were calculated according to normalized transmittance data obtained from Z-scan setup with closed and open aperture. The effect of the laser dye type changing in thin films of the same contents had been studied. The main conclusion is that the Rhodamine B laser dye give highest linear and non-linear optical properties than Styryl 9M laser dye. This can be attributed to that the first has more complete Benzene rings than for second and causes more absorption. So, this helps in choosing the medium and Fe3O4 nanoparticles with appropriate excitation wavelengths.