A mechanical lock core of arc strip key contains inner lock core sleeve (10), outer lock core sleeve (90) and key (30). Several rotary round lock blades (20) are stacked into (10). Triangle lock shafts (21) incurving toward axis are opened on excircle of (20) and two bumped backstop (22, 23) are set on its circle. The (30) is strip with dental alveolus (31) toggling (20) to rotate on one side. When all (21) are alignment, the plunger latch (40) drops into the (21) and (10) can rotary freely to lock or unlock. The tooth figures can be up to 100 hundred million or above, which improve the confidentiality of mechanical lock greatly. It can prevent unlocking by violent methods such as prying and drilling etc. effectively to improve the security of mechanical lock.