A fast and non-invasive method for determining the mixture percentages of brake fluid based on visible and near infrared spectroscopy (Vis--NIRS) was proposed. Both a partial least square regression (PLSR) model and a least-square support vector machine (LS--SVM) model were established according to the spectra obtained in the whole wavelength range. With those two models, good prediction results were obtained. The determination coefficients of their calibration and prediction sets (r2c and r2p) were greater than 0.98. The successive projection algorithm (SPA) was used to select the effective variables. Finally, eight variables of 439 nm, 443 nm, 459 nm, 519 nm, 570 nm, 717 nm, 896 nm and 902 nm were selected as the optimal variables to be input into the PLSR and LS-SVM models. The r2c and r2p of both two models were greater than 0.97 which was adequate for practical application. It was concluded that Vis-NIRS could be used to fastly and non-invasively determine the mixture percentages of brake fluid.