Effects of bacterial lipopolysaccharide (LPS) and dopamine (DA) on phagocytic activity, exocytosis and signal transduction of haemocytes in white shrimp (Litopenaeus vannamei) were studied. The haemocytes treated with LPS (1-10 mg/L) and dopamine (1-10 μmol/L) in vitro showed conspicuous dosedependent decrease in cell count, and increase in extracellular phenoloxidase (PO) activity. Phagocytic activity of haemocytes was promoted by LPS and inhibited by dopamine. Meanwhile, the addition of chelerythrine (a PKA inhibitor) and genistein (a TPK inhibitor) to haemocytes can inhibit phagocytosis and exocytosis induced by LPS, and the inhibitory efficiencies on phagocytosis and exocytosis respectively were: genistein＞chelerythrine, chelerythrine＞genistein. Dopamineinduced cell phagocytosis was strenghtend by H89 (a PKA inhibitor), its exocytosis was inhibited by chelerythrine and genistein, and the efficiency was chelerythrine＞genistein, and the two inhibitors had no impact on dopamineinduced phagocytosis.