Abstract:  Objective To investigate the numbers, sizes and types distribution of diatoms in drowned and postmortem immersed rabbits’ lungs. Methods Sixty-two rabbits were randomly divided into drowning group （n=30）, postmortem immersion group （n=30） and land death group （n=2）, and the diatoms in each lung lobe were analyzed quantitatively and qualitatively by microwave digestion and scanning electron microscopy. Results In the drowning group, the diatoms were detected in each lung lobe with Cyclotella and Melosira in the majority. In the postmortem immersion group, Cyclotella was in the majority. And the diatoms weren’t detected in some lung lobes in postmortem immersion. There were significant differences in the detection rates of upper lobe of left lung, middle lobe and cardiac lobe of right lung in two groups （P<0.05）. Conclusion Based on the microwave digestion and scanning electron microscopy, the numbers, sizes and types distribution of diatoms in drowned and postmortem immersed rabbits’ lungs can be analyzed and used as references for testing theory.

Key words: forensic pathology, drowning, diatoms, rabbits