The purpose of this report is to study the characteristics of the hemocytes of Meretrix lusoria. A medium-size clam (body length 4.5-5.5cm) contained 4.40 ± 1.26ml of body fluid which had an osmolarity of 502.2 ±21.5 mOsm. Hemocyte count of body fluid was 1291 ±354/mm3. There were three types of hemocyte, type 1 (He-1, 8-12μm) had pseudopodia and showed amoeboid movement; type 2 (He-2, 2-4Ilm) had smaller cell body with thread-like pseudopodia; type 3 (He-3, 15-19μm) had granules in cytoplasm. The proportion of three types of hemocyte (He-l to He-3) was 7S%, 20% and 5% respectively. During storage at low temperature (4 ± 1℃), hemocyte count of body fluid, both in vivo and in vitro, decreased significantly with the times. However, contents of reduced sugars of the body fluid did not show significant changes.