Composting treatment is a key method of processing organic solid waste, especially for agricultural organic solid waste. Aiming to study the feasibility of several selected variables from near infrared spectroscopy to quantify humic acid in compost, determine composting fermentation and develop corresponding control equipment to provide theoretical basis by near-infrared diffuse reflection spectrum. Totally 100 composting samples were collected, including 58 samples for calibration and 42 samples for validation. On the one hand, the humic acid of these samples were analyzed by using the International Humic Substances Society standard of humic acid method, on the other hand，those were scanned to obtain near infrared spectra with the wavelength range of 4000~9000cm-1. Both of spectroscopic pre-treatment method and sensitive variables were optimized, and then the model was built by partial least squares regression method．The results indicated that humic acid in compost can be determined by near-infrared(NIR) spectral technique, because they were combined with organic groups with NIR absorption. A method for the determination of humic acid in compost samples was established based on the combination of discrete wavelet transform (DWT) and NIR technique. In the proposed method, the raw NIR data and their wavelet coefficients were used for modeling and prediction of the contents of humic acid in compost by partial least square method (PLS). The model based on wavelet coefficients was better than that based on the full NIR spectral range. With the improved method, accurate prediction can be achieved. 