The invention discloses a kit and method for measuring the content of free fatty acid. Reagents of the kit comprise the first reagent composed of isooctane, the second reagent formed by dissolving sodium acetate in distilled water, then adding pyridine and mixing the constituents uniformly and the third reagent formed by dissolving copper acetate in distilled water, then adding pyridine and mixing the constituents uniformly. The method comprises the steps that free fatty acid in a sample is extracted through the isooctane, then the free fatty acid reacts with copper salt to generate copper soap under the weak acidic condition, and the content of free fatty acid in the reaction sample at the light absorption value of 715 nm is measured. According to the method, based on measurement conducted through an existing colorimetric method, the extraction method and operation steps are improved, and the effects of simple extraction and fast, simple and convenient measurement are achieved. According to the method, the sample pre-treatment process is simple and convenient, and an extracting solution is singular in constituent and low in cost. According to the measurement steps of the method, only the three reagents are needed for completing measurement, and the process is simple, convenient and fast.