An anti-theft automobile steering wheel lock with an alarm unit includes a stationary base, an insert pin, a helical spring, a locking core, a movable constrict base, an alarm unit and a cover. The locking core can be rotated with a key to let a projecting member move downwards to separate from a fitting hole so that the helical spring extends to push up both the insert pin and the locking core outwards. Meanwhile, the separation of the insert pin away from an insert hole of the telescoping rod enables the movable constrict base moved farther away from the stationary base, unlocking the lock. Reversely, pushing the locking core inwards into the stationary base can lock the lock on the steering wheel, and simultaneously the alarm unit started.