Objective: A formaldehyde detection method was established for the accurate analysis of the migration of formaldehyde in water and acid simulants from the polylactic acid straws. Methods: The preferred chromatographic conditions were: mobile phase water-acetonitrile (V_water∶V_acetonitrile of 55∶45), column temperature of 35 ℃, detection wavelength of 355 nm. The optimized 2,4-dinitrophenylhydrazine derivative conditions were: the acetic acid in acidic 2,4-dinitrophenylhydrazine solution of 1.5 mL/100 mL (pH 3.07), the molar ratio of 2,4- dinitrophenylhydrazine of quadruple formaldehyde, the reaction temperature of 45 ℃, and the reaction time of 40 min. Results: The linear equation of formaldehyde-2,4-dinitrobenzene was y=55.247 0x-3.849 4 within 1.008 to 70.560 μg/mL, with the correlation coefficient of 0.999 5. The detection limit of the corresponding formaldehyde was 0.066 mg/kg, and the quantification limit of which was 0.22 mg/kg. The formaldehyde-DNPH was stable within 13.5 hours. The average recovery of simulants spiking with formaldehyde in 3 levels was from 92.6% to 104.1%, with SD (n=6) of 0.4% to 3.3%. The maximum migration of formaldehyde from disposable polylactic acid straws to three food simulants (water, 3% acetic acid solution, 4% acetic acid solution) was 1.839 mg/kg, less than the specific migration requirement of 15 mg/kg stipulated by China and the European Union. Conclusion: This method is accurate and efficient enough to apply for the analysis of formaldehyde migration from polylactic acid straws.