The invention discloses a method and system for evaluating material liquid quality stability and relates to the field of chemical analysis detection. The method comprises infiltrating a color development test paper with a material liquid sample to be tested, immersing a blank test paper in a preset solution for appointed time, airing the blank test paper to obtain a development test paper, dissolving methyl red, ethoxychrysoidine Hydrochloride and sodium hydroxide through an ethanol aqueous solution with a predetermined concentration according to a preset ratio, adjusting the pH of the solution to a predetermined pH to obtain a desired solution, acquiring a near-infrared spectrogram of the development test paper, calculating a Mahalanobis distance of the near-infrared spectrogram in a principal component vector space, and determining that the detected material liquid has stable quality when the Mahalanobis distance is less than a Mahalanobis distance threshold value of the material liquid sample to be tested. The method and system can be operated simply, are free of additional treatment on the sample, take full advantage of the near-infrared detection technology, have high accuracy of the detection result, realize full recovery and utilization of the residual liquid material after the secondary blending, and reduce enterprise production costs.