Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体">Aggregation of zinc oxide (ZnO) nanoparticles in its synthesis process as well as its antibacterial perfor-mance were discussed.ZnO nanoparticles were synthesized by precipitation method assisted with sodium tripolyphosphate (STPP) as surfactant.Samples had been characterized by XRD,TEM,TG-DTA,and BET.Results showed that prepared ZnO crystals were highly dispersed <SPAN style="mso-spacerun: yes">&nbsp;</SPAN>spheroidal particles which belonged to single crystals with a hexagonal wurtzite structure;their were 20 nm in diameter on the average,and BET surface area reached 70.478 1 m2/g.Precursors were formed through homogeneous nucleation reaction in complex effect of linear STPP with Zn<SUP>2+</SUP>,and steric hindrance repulsion between particles prevented nanoparticles from agglomerating.Antibacterial activity of ZnO nanoparticles were determined by cup me-thod. Results showed that ZnO nanoparticles had distinctive antibacterial activities to Staphylococcus aureus,Escherichia coli,and Salmonella,and antibacterial activity of ZnO nanoparticles was decided by the specific surface area.</SPAN><SPAN style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"; mso-bidi-font-family: "Times New Roman"; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"></SPAN>