The utility model relates to an oil and gas separating device for reducing pollution caused by heat release in a long oil product transporting pipeline. According to the device, an oil and gas gathering tank is connected to a heat release valve outlet of the long oil product transporting pipeline; a heat release valve outlet pipeline is connected between the heat release valve outlet and a gas inlet of the oil and gas gathering tank. By adopting the technical scheme, the situation that the backpressure of a heat release device is too high can be effectively improved, the oil and gas separation can be realized and the separating effect is up to more than 95%; the device meets the requirements of environmental protection and is simple in operation, free of power source consumption and low in use cost. The technique is already applied to multiple two-end cutout valves and engineering that the pipeline length is greater than 80 meters. Compared with a common oil and gas recovery mode, the device has the advantages that the production cost can be reduced to a large extent; the ground pollution and the air pollution are avoided so as to achieve the purpose of protecting the environment.