The detection method for ethanol vapor concentrationin air based on tunable diode laser absorption spectroscopy is studied using narrow absorption peak in the vicinity of 7180 cm-1 (1393 nm) as an identification feature of ethanol molecule. To eliminate the interference of coexisting water vapor with the detection for ethanol vapor concentration in air, multidimensional linear regression analysis is applied to solve the problem of the coexistence of multiple molecule absorptions. A modification equation is promoted to resolve the problem of spectral error in the spectral data processing procedure, which is proved by experiments. The detection limit of integrated concentration is obtained by open-path measurement experiments as 30×10-6 m.