In view of the fact that other harmonic components besides the second harmonic still contain concentration information,three concentration inversion methods based on 2nd-/4th-harmonics, 2nd-/4th-/6th-harmonics, and 2nd-/4th-/6th-/8th-harmonics, as well as their corresponding expressions, are presented while the optimal value of the modulation depth for each inversion method is evaluated. The main forms of noise interference in gas concentration detection systems are also analyzed and the usefulness of multiple harmonic analysis for noise suppression is proved theoretically. Finally, an experimental verification scheme is given for reference. Our simulation's results indicate that the above methods can reduce concentration inversion errors by 31.38%, 42.03%, and 47.45%, respectively, as compared with the 2nd-harmonic-based method.