Deoxynivalenol (DON) is a mycotoxin that often occurs in cereals and their derivatives. It is harmful to the life and health of human and livestock. It is urgent to develop a detection method, which can rapidly, accurately and economically detect DON without environmental hazard. This study defined a Trend Parameter (TP) of the visible-near-infrared (VIS-NIR) spectra. The TP was used to determine the characteristic bands which were most relevant to the DON concentration. In this paper, the rows of spectral matrix of the samples in calibration set were arranged in the order of gradual increase in DON concentration. Each column (each band) of the matrix corresponded to a TP value. Under a certain band, the stronger the increasing trend of the absorbances of all samples in the column direction is (ie, the larger the TP value), the stronger the correlation between the absorbance and the DON concentration in this band is, and this band can be used as a characteristic band for evaluating the DON concentration. The study found that the local maximum of TP appeared at 666, 1 238, and 1 660 nm. The quadratic discriminant analysis (QDA) was performed by the spectra of the three characteristic bands. The wheat flour can be divided into three grades: mild (0