A more stable and reliable method of the fatty acid values determination in grain was studied based on the establishment of manual titration method associated with the automatic potentiometric titration. The GB/T 20569—2006 Guidelines for evaluation of paddy storage character for the sample pre-treatment was used, and the manual titration was replaced by automatic potentiometric titration to determine the free fatty acid in grain with KOH as the standard titration solution. At the same time, the change of pH values in test solution were determined during titration, following by the corresponding real time change curves of pH-titration volume which will be stopped at the set terminal PH values, and phenolphthalein indicator was used as the finish monitoring in the process of the titration. The results showed that the titration processes were not affected by man-made factors, and the accuracy has no significant difference compared with manual titration method, thus ensuring the determination results has better repeatability, reproducibility and stability, and with the wider application scope.