Tetraammine-cis-bis(5-nitro-2H-tetrazolato-N2) cobalt (Ⅲ) perchlorate (BNCP) superfine particles were obtained with fluid milling and cryogenic drying methods. The results show that their morphology become round and smooth,their particle sizes distribute from submicron to 2 μm,their surface areas increase from 0.087 m²·g^-1 to 10.8 m²·g^-1,and their impact sensitivity and friction sensitivity decrease.