The invention discloses a method for detecting fatty acid content in rice fat. The method comprises the following steps of: carrying out base-catalysis methyl esterification and solid phase microextraction synchronously on a rice sample in a headspace bottle by means of a multifunctional sample injector, and then detecting and performing quantitative analysis on the fatty acid content in the rice fat after the rice sample enters a gas chromatography-tandem mass spectrum (GC-MS-MS). According to the invention, the on-line methyl esterification, the solid-phase microextraction and the gas chromatography-tandem mass spectrum technology are adopted, the five steps of methyl esterification, extraction, enrichment, sampling and detection are completed at the same time during one process, the operation is simple, and the consumed time is short; moreover, water acts as a base body during the methyl esterification reaction, so that the competitive adsorption of an extracting head to methyl alcohol and volatile substances is lowered, and the extraction and pre-enrichment of fatty acid methyl ester by the solid phase microextraction are improved effectively; and the minimum detection limit of fatty acid is 0.001-0.049 micro g/L, and is obviously lower than the minimum detection limit, 4.0mg/L, of an internal standard method which is used for performing quantitative determination on oil fatty acid.