The invention relates to a detection method and system for alcohol content in a human body on the basis of a near infrared spectrum. The detection system comprises a light source, an optical fiber probe, a data processing module and a digital display module. According to the quantitative relationship of the near infrared absorption spectrum of the group of keys, such as C-O, C-C and the like of an alcohol molecule and alcohol content, an alcohol reflection spectrum in skin and blood is detected by an optical sensor probe; and after the alcohol reflection spectrum is subjected to wavelet analysis and noise removal, a quantitative relationship between the spectrum characteristic of the human body alcohol and the alcohol content is built, and a partial least square (PLS) correction model is built so as to achieve the purpose of detecting the alcohol content in the human body.