In order to realize the identification and content determination of methanol/ethanol diesel, the methanol diesel and ethanol diesel are prepared in the laboratory and divided into two groups by principal component analysis. Based on the mid-infrared spectra method, the preprocessing spectra are produced by smoothing, baseline correction, multiplicative scatter correction and normalization of the spectral data. The least squares support vector machine (LSSVM) prediction model is used to predict methanol/ethanol content, and the error rate is lower than 7.1%. The simulated results show that the correlation coefficient and the mean square error of the LSSVM prediction for methanol content of methanol diesel are 0.9791 and 1.7201; the correlation coefficient and root mean square error are 0.9802 and 2.9563 for ethanol content of ethanol diesel, respectively. The experimental results show that the proposed model is a promising choice to identification and content determination of methanol/ethanol diesel.