Infrared thermography is a non-contact measurement method which is widely used in human body temperature monitoring. But there are still some limitations when infrared thermography is used in medical diagnosis, so the accuracy of infrared thermal imaging is still being debated. Spectroscopic analysis is a powerful technology. It not only can reflect the relative temperature difference accurately, but also can get the energy information of human body at different spectral coverages. We measured the infrared radiation spectrum (Spectral Range: 1.33μm~16.67μm) of human body by using high precision spectrometer, and found some interesting results. The regular changes of the infrared radiation spectrums which are measured at different time have been discussed in this paper. More information about the human body condition can be gotten from these regular changes. Our Future work will focus on the correlation between the radiation energy distribution changes of spectrum and the physiological changes of human body.