Hemocyte types of the Macrobrachium prawn Macrobrachium rosenbergii were identified using the methods of flow cytometry and light microscopy. The activities of endoenzymes including peroxidase (POD), phenoloxidase (PO), and alkaline phosphatase (ALP) in hemocytes were analyzed by cytochemical and biochemical methods. Mitochondrial membrane potential (MMP) of the hemocyte was probed according to the accumulation of the cyanine dye, 3′, 3′-dihexyloxacarbocyanine iodide, in the mitochondrial matrix. The results showed that there were three types of circulating hemocytes (hyalinocytes, semigranulocytes, and granulocytes) in M. rosenbergii. Enzymes POD, PO, and ALP were more abundant and active in granulocytes and semigranulocytes than in hyalinocytes. The data associated with MMP showed that the fluorescence intensity in the hemocyte was directly correlated to cell complexity. The MMP in granulocytes was significantly greater than that in semigranulocytes, and the latter was significantly greater than that in hyalinocytes.