High performance liquid chromatography (HPLC) was applied to the determination of formaldehyde in muscle tissues of sea fishes. The samples were soaked with distilled water for 30 min, and then heated in phosphoric medium. Formaldehyde was absorbed by water using steam distillation method. The collection was taken and derived with 2, 4-dinitrophenylhydrazine under the condition of 60 ℃ water bath for 20 min．The derivative was determined by HPLC after rapid cooling. In the range of 0.20-15.0 mg/L, linear correlation coefficients were all above 0.999 9. And in the range of 2.0-20.0 mg/kg, the mean fortification recoveries were between 92.5% and 98.0%, The RSDs were all less than 5.0%, and the detection limit was 0.20 mg/kg. The method had little matrix interference, proper target peak, and higher repeatability and stability.