Diabetes is a kind of diseases which does harm to people’s health, and the detection of human blood glucose levels utilizing blood samples will result in pain even infection for patients. Thus the in-vivo noninvasive measurement of human blood glucose levels has vital value in clinical diagnosis, detection and therapy, and it also is a very hot research topic with challenging. At present, as to various noninvasive detection methods, the technology based on mid-infrared absorption spectrophotometry with ATR has been gaining increasing attention. However, when carrying out noninvasive measurement of human blood glucose levels by means of the spectrophotometry equipped with routine light sources, the penetration depth of probe light in human tissues is low and thus it is very difficult to reach the stromal layer containing body fluids and especially dermis layer containing blood for probe light, which resulting in low relativity between experimental data and real human blood glucose levels and thus limiting the clinical application. Generally, not only the mid-infrared laser with high strength and high purity can deeper penetrate the human tissues, but also the output wavelengths at 1 035 cm-1of CO2 laser very coincide with the fundamental frequency characteristic absorption at 1 029 cm-1of glucose. Thus, in this work, a novel noninvasive mid-infrared measurement system to detect human blood glucose levels has been successfully assembled, in which a CO2 laser was used a self-defined external light source of the new mid-infrared absorption spectrophotometry with ATR. In this system, the absorbance of human fingertip at 1 035 cm-1 has been measured when external CO2 laser source was used as probe light, at the same time, the mid-infrared absorption spectra of fingertip have been also obtained and absorbance at 1 492 cm-1 has been recorded. The human blood glucose levels were determined synchronously by means of the routine medical method. The experimental results showed that the ratio in fingertip between absorbance at 1 035 cm-1 from the laser source and one at 1 492 cm-1 from mid-infrared absorption spectrophotometry could synchronously change with the human blood glucose levels, and the ratio presents certain positive relativity with the real human blood glucose levels（R=0. 812 5）. Thus the measurement data could be used as a new index of blood glucose level in human body, which showed the potential in clinical diagnosis of the ATR mid-infrared absorption spectrophotometry with external CO2 laser source in noninvasive measurement of human blood glucose levels.