Neutrophil Activating Protein 3 (NAP3) ,also known as chemokine (C-X-C motif) ligand 1 (CXCL1) is a small cytokine belonging to the CXC chemokine family. NAP3 plays a role in spinal cord development by inhibiting the migration of oligodendrocyte precursors and is involved in the processes of angiogenesis, arteriogenesis, inflammation, wound healing, and tumorigenesis. Thus, chemotaxis assay used 24-well microchemotaxis system was undertaken to detect the chemotactic effect of NAP3 on the human monocytic cell line THP-1. Briefly, THP-1 cells were seeded into the upper chambers (100uL cell suspension, 5×105 cells/ml in RPMI 1640 with FBS free) and recombinant human NAP3 (0.01ng/mL, 0.1ng/mL, 1ng/mL, 10ng/mL, 100ng/mL, 1000ng/mL diluted separately in serum free RPMI 1640) was added in lower chamber with a polycarbonate filter (8um pore size) used to separate the two compartments. After incubation at 37℃ with 5% CO2 for 1h, the filter was removed, then cells in low chamber were observed by inverted microscope at low magnification (×100) and the number of migrated cells were counted at high magnification (×200) randomly (five fields for each filter). Result shows recombinant human NAP3 is able to induce migration of THP-1 cells. The migrated THP-1 cells in low chamber at low magnification(×100) were shown in Figure 1. Five fields of each chamber were randomly chosen, and the migrated cells were counted at high magnification(×200). Statistical results were shown in Figure 2. The optimum chemotaxis of NAP3 occurs at 0.1~1ng/mL.