The present invention relates to a lock and a key for the same, and multiple modular lock core units are mounted in the lock. Multiple lock bead units having specific standard are mounted in each lock core unit. Each lock bead unit is detachable and is able to rearrange the permutations of the lock bead units. The key includes a handle, a core bar and multiple unlocking blocks. The core bar is connected with the handle. The unlocking blocks are detachable, are mounted around the core bar and have multiple lock teeth sequentially formed around the inner peripheries of the unlocking blocks. A user can adjust the permutations of the key teeth of the key to unlock the lock that has different permutations of the lock bead units, also can change the permutations of the lock core units to get the same effects.