The present invention relates to a lock core, particularly relates to a theft-proof lock core. The technical scheme of the invention is as following: a theft-proof lock core includes a lock case and a lock core which is provided with a plurality of billiards hole in rows, wherein each billiards hole provided with one billiards inside, the lock case is provided with sealing bead and suppress spring, lock bead is provided between the suppress spring and billiards, a loading trough is set on transversal global face of at least one billiards, a locking key is set between lock core and lock case, locking key fits with loading trough on billiards, locking billiards is set inside the billiards hole between lock core and billiards which connects with billiards socket joint and slides along its axial direction, an opening is set on terminal side of locking billiards facing the locking key which fits with lock key and communicates with loading trough on billiards, ball lump is provided between at least one billiards and lock bead, a groove is provided on neighbor face of lock core and lock case which fits with the ball lump. A theft-proof lock core with high security is provided through above technical scheme of the invention.