Objective: To study characterization difference of Realgar after smashed by ultra-high pressure jet and investigated the influence of particle size to antibacterial effect. Method: Smashed Realgar by ultra-high pressure jet technology

and compared powder characterization and in vitro antibacterial effect of ordinary powder

levigating powder and jet powder of Realgar. Result: Compared with ordinary powder and levigating powder

average particle size of jet powder reduced from 23.756 μm to 1.427 μm

specific surface area increased from 1.251 m2·cm-3 to 11.653 m2·cm-3

angle of repose increased

and bulk density decreased

main chemical composition had no significant change;Minimum inhibitory concentration (MIC) to escherichia coli reduced from 8% to 2%

MIC to staphylococcus aureus reduced from 1% to 0.5%. Conclusion: After smashed by ultrahigh pressure jet

particle size of Realgar ultra-high pressure jet powder reduced significantly

specific surface area significantly increased

porosity increaseed greatly

liquidity got worse

main chemical composition of the powder complied with pharmacopoeial requirement

in vitro antibacterial effect and powder particle size was negatively correlated. The result showed that smashed Realgar by ultra-high pressure jet was feasible.