Objetlhte: To abody the effect of sodium tanshinone II A sLllfonate(DS-201) on calcium-activated polaseium chan-nels(kc. of poreine ooronary amooth muscle cells. Methods: Compared with comtrol(before drug).the changes of the properties ofthe channels after application of DS-201 (sodium tanshincme II asudonate) were irwestigated using patch clamp technique. Re-surts: It was demonstrated that:(1) the kca channels high conduclance of 291.74pS and were aensitive to both membrane po-tontial and [Ca2+] and blocked by TEA; (2)in cell-arttached patches, DS-201 0f 5-30pmol/L had no effect on Kca channela;while in inside-out patches, the Kca channels were significantly activated by DS-201 of 5～20igmol/L. Condusion: DS-201 acti-vated Kca cIIfmnels by a direct mechanism.