Abstract: In order to measure thickness accurately, it’s important for the X-ray thickness measurement equipment to be demarcated using some reference samples. The more reference samples are taken, the more accurate the calibration curve is; but the system cost will be higher in the same time. Based on the profile gauge for steel strip, X-ray spectrum was generated using the TASMIP method. By analyzing the attenuation principle of the spectrum in the steel strip, the series of the reference samples was calculated. The thickness series, which could be used in practice was given.