The utility model discloses an opening mechanism on an automobile armrest box, which comprises a box body and a box cover, two lock keys are respectively arranged on the left side and the right side above the box body, two double-side locks are respectively arranged on the left side and the right side inside the box cover, each double-side lock comprises two lock rods which are symmetrically arranged, and the lock rods are in sliding connection with the box cover in a matched mode. The outer ends of the lock rods penetrate through the box cover and can stretch out and draw back, connecting rods are hinged to the inner ends of the two lock rods respectively, the inner ends of the two connecting rods are hinged through a support, the support is of a rod-shaped structure, keys capable of stretching out and drawing back transversely are installed in the middles of the left side and the right side of the box cover, and the other end of the support is connected with the keys. The lock rod penetrates through the guide sleeve and is in sliding connection with the guide sleeve in a matched mode, a spring is installed on the lock rod, the inner end of the spring is connected with the end of the guide sleeve, and the spring exerts outward thrust on the lock rod. The two sides of the armrest box cover can be opened, so that articles can be taken and placed from any one of the two sides, and the use convenience is improved.