Tetraammine-cis-bis (5-nitro-2H-tetrazolato-N²) cobalt (Ⅲ) perchlorate (BNCP) superfine particles were obtained by fluid milling and cryogenic drying methods with absolute ethanol as non-solvent. Their particle sizes were mostly under 2 microns and their surface area were from 3.88 m²?g^-1 to 13.9 m²?g^-1. The results show that their impact sensitivity and friction sensitivity decrease with increase of surface area. Electrostatic sensitivity of superfine particles is higher than that of origin particles while they change indistinctively with increase of surface area. DSC exothermic onset temperature and exothermic peak temperature become lower with the increase of surface area.