The invention discloses a cooling device and system of a rail side detector. The cooling device comprises a box body (3), an air pump (6) and a tuyere (8). The box body is used for packaging the rail side detector, the air pump (6) is used for pumping high-temperature gas inside the rail side detector, and the tuyere (8) is located inside the box body (3), and is connected with an air inlet (7) of the air pump (6) through an air sucking pipeline. According to the cooling device and system, the cooling device is additionally arranged on an existing rail side detector, and the problem that due to strong sunlight exposure in summer and high-temperature weather in hot seasons, an axle temperature scanner inside the rail side detector cannot normally work is solved.