A HPLC method with online pre-column derivatization for determination of γ-amino butyric acid (GABA) in germinated brown rice was established. The germinated brown rice sample was extracted two times by ratio of solid to liquid 1∶5, ultrasonic power account for 60% of total power, at 30℃ for 30min. Online pre-column derivation 2min were reacted by using orthophthalaldehyde (OPA) derived reagents and sample after mixing 10 times. The sample was separated on an Agilent Eclipse Plus C18 column（at 1.0mL/min, 338nm and 40℃）.Good linearity was observed in the range of 5～50mg/L with the correlation coefficient＞0.9990; minimum detection limit 0.33mg/L, minimum quantitative detection limit of 1mg/L, fortified recovery 94.80%～98.40%, RSD 1.82%～2.58%. The proposed method is simple, rapid, sensitive, accurate and suitable for the detection of GABA in germinated brown rice.