The utility model relates to an oil and water separator, belonging to a liquid separation device, and obtains the goal of separating the oil in a cooling liquid tank from the cooling liquid so as to ensure the normal cooling effect of the cooling liquid. The oil and water separator comprises a power device, a transmission device, an oil and water separating device and a shell. The transmission device includes a drive shaft, a tension shaft, a drive roller, a tension roller and an oil sticking tape. The oil and water separating device includes an adjustable oil scrapping plate and an oil separating box. A tension device is additionally installed at one end of the tension shaft to always keep the oil sticking tape in the tensioned state and to facilitate the oil scrapping plate to scrap oil from the oil sticking tape. The oil and water mixture scrapped from the oil scrapping plate is put into the oil separating box for secondary separation by using the specific weight difference of the oil and the water, thereby improving the separation effect and the utilization ratio of the cooling liquid. An immersion depth adjusting mechanism is installed at the two sides of the shell. The immersion depth adjusting mechanism is used to adjust the immersion depth according to the level of the liquid in the cooling liquid tank, so as to always keep the collecting face of the oil sticking tape below the liquid level and improve the practicability.