The invention discloses a small laser receiving device under a strong magnetic environment, which includes a mounting base, a receiving objective lens and a receiving circuit. The mounting base is ofa 90-degree sector structure, and is provided with a mounting slot at the sector arc end thereof. The receiving objective lens is fixedly connected into the mounting slot, and the width of the mounting slot is larger than the receiving scope of the light path of the receiving objective lens. The mounting base is internally provided with a mounting cavity. The receiving circuit is arranged in the mounting cavity, and is used for converting an optical signal received by the receiving objective lens into an electrical signal. The arch structure in the middle of the receiving objective lens is composed of multiple sections of spherical mirrors lapped one on another. The outer surface of the lens of each section of spherical mirror is a Tschelning ellipse, and the inner surface is a planar square. A shielding sleeve is also arranged in the mounting cavity. The laser receiving device of the invention is small, costs low, and has a simple structure. The laser receiving device is resistant tointerference in a strong magnetic environment. It is ensured that a laser detection system can work normally in a strong magnetic environment.