Abstract: A technique of errors treatment is presented according to the negative impact of systematic errors, which is hard to eliminate in photometric measurement data, on the characterization accuracy of thin film optical parameters. In order to minimize the characterization deviations of thin film optical parameters from the real values caused by photometric measurement systematic errors, it is advised to select the photometric measurement data used in optical characterization from spectral bands characterized with opposite signs or single zero of first-order spectral coefficients partial derivatives with respect to layer thickness and refractive index for most measurement incident angles, and to exclude spectral bands characterized with the same signs or both zeros of spectral coefficients first-order partial derivatives for all measurement incident angles. The essence of this technique is to minimize the errors transfer effect of measurement data on thin film optical parameters characterization by spectral band selection with first-order partial derivatives analysis. Numerical simulations have been conducted to investigate its applicability to characterization with different polarization lights and the skills in selection of the range of measurement incident angles. The reliability of this technique is supported by replicable numerical experiments and reasonable theoretical explanations.