In order to solve the shortcomings of mutual interference between spectra and slow modeling speed,a multi-band weighted combination model combined with the partial least squares (PLS) method was used for quantitative analysis to improve the measurement accuracy.In this paper,a gas detection system based on spectrum laser absorption spectrum (SCLAS) was built to perform a weighted combination measurement of CO₂ in different wavelengths of the near-infrared based on PLS.The absorption spectra of different concentrations of CO₂ in the bands of 1425—1443 nm,1565—1587 nm,and 1595—1616 nm were measured at room temperature and pressure.The single-band regression model based on PLS was established,and the coefficient of determination (R²) were 0.9897,0.9486 and 0.9497,respectively. The weights of the single band models are determined based on R² and the root mean square error (RMSE).A new PLS combination model is established using the multi-band weighted combination model algorithm,and the obtained R² are 0.9852 and 0.9912,respectively.The experimental results show that the PLS-based weighted combination model can improve the accuracy and stability of CO₂ concentration prediction and effectively avoid the slow modeling speed and interference problems.