The invention discloses an oral-cavity fixing device. The oral-cavity fixing device comprises first support rods, a rotary shaft, handles, a first fixing sleeve, fixing parts, a second support rod, first protrusions, a slider, a thin rope, a second fixing sleeve, grooves, first springs, second protrusions, retaining blocks and second spring. The oral-cavity fixing device has the advantages that the grooves are arranged in the top surface of the arc-shaped first fixing sleeve and the bottom surface of the second fixing sleeve, teeth are located in the grooves when the device is used, and the tip of the tongue can be prevented from being bitten by the teeth; the first fixing sleeve and the second fixing sleeve are fixedly connected with the fixing parts, and the fixing parts clamp the handles; when the device is used, the handles are pressed down to compress the springs inside the first support rods to reduce the distance between the fixing sleeves, a person can conveniently bite the grooves, the springs reset when the handles are released to allow the fixing grooves to distract the oral cavity, the first protrusions on the lateral walls of the second support rods are abutted againstthe second protrusions to fix the second support rods so as to fix the oral cavity, the handles are taken out from the fixing parts, and medical equipment can conveniently move inside the oral cavity.