Abstract: An electronic lock cylinder, includes a mechanical rotation core, electronic rotation core, barrel-shaped housing with both ends opened for accommodating the rotation cores, and a retainer rod, the rotation cores fixed axially to each other via an electromagnet core, and the mechanical rotation core and the housing fixed to each other via the retainer rod. When the core is retracted, the rotation cores can rotate through a certain angle with respect to each other, and the retainer rod is moved such that the rotation cores are fixed to each other and rotate together, now rotating the electronic rotation core by using an electronic key, and a deflector rod of the mechanical rotation core is driven to rotate such that the lock is unlocked. Further disclosed are an electronic lock system including the electronic lock cylinder and a method for unlocking a lock. Axial fixation between the rotation cores is achieved.