This study presents a method for correcting light intensity in light⁃induced thermoelastic spectroscopy (LITES) using a nonlinear light intensity response, enabling precise light intensity corrections. The DFB laser, set to a wavelength modulation mode at a frequency of 16369.75 Hz, benefits from enhanced nonlinear light intensity due to a fiber amplifier. The laser beam traverses a multi⁃pass cell before focusing on the quartz tuning fork (QTF) base, generating a thermoelastic signal. A lock⁃in amplifier demodulates the harmonic signal, and polynomial fitting of the harmonic signal's baseline extracts harmonics related to both concentration and light intensity. Experimental data reveal a strong linear correlation (coefficient > 0.998) between the baseline amplitude of the harmonic signal and light intensity as it varies from 22.03 mW to 3.16 mW, with normalized harmonic signal amplitude variation under 0.37%. In methane detection, the system demonstrates a robust linear response across a broad concentration range, with harmonic signal noise ratios indicating a detection threshold as low as 0.22×10^-6. This research offers a novel approach for LITES light intensity correction, significantly enhancing system stability for prolonged measurements.