The invention discloses a protective film with a fingerprint unlocking function and a preparation method thereof. The protective film solves the problem that a mobile phone screen protector cannot protect a fingerprint unlocking sensor, and is easy to produce in batches. The protective film disclosed by the invention comprises a PE film, a hardened layer, a PET base material, a pressure-sensitive coating layer and a PET separate film from top to bottom; the pressure-sensitive coating layer is 10 to 20 microns in thickness; the PET base material is 2 to 25 microns in thickness; the hardened layer is 1 to 2 microns in thickness. The protective film is low in cost and convenient to implement, and can guarantee rapid and normal operation of the sensor.