Eighty pieces of liver tissues were collected, each piece of tissue was 2 g, and 2 mL Pearl River water was added to each piece of tissue. The digestion temperature was set at 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃ and the digestion time was set at 40, 50, 60, 70, 80 min. The liver tissue and water mixture were divided into 8 portions in each group. All the samples were tested by microwave digestive - vacuum filtration - automated scanning electron microscopy method. The quantity of diatom recovered and the quality of residue on the membrane were recorded.

When the digestion time was set to 60 min, there were statistically significant differences in the number of diatoms recovered at different temperatures （P<0.05）. The maximum number of diatoms recovered was （28 797.50±6 009.67） at 140 ℃, and the minimum residue was （0.60±0.28） mg at 180 ℃. When the digestion temperature was set at 140 ℃, there were statistically significant differences in the number of diatoms recovered at different digestion times （P<0.05）. The number of diatoms recovered was the highest at 40 min, it was up to （20 650.88±1 950.29）, and the residue quality of each group had no statistical significance among different digestion time groups（P>0.05）.

The effect of diatom digestion is related to temperature and time. When the digestion temperature was 140 ℃ and the digestion time was 40, 50 and 60 min, it is favorable for diatom test.