The invention relates to a combined type oil-water separating system for onshore treatment stations and offshore oil production platforms, wherein a liquid inlet and a liquid outlet of a current divider are communicated with a horizontal total liquid inlet pipe, a vertical pipe and a lower horizontal pipe; the vertical pipe is communicated with a bend pipe; the lower horizontal pipe is connected with an input port of a helical pipe, the helical pipe is connected with the inner part of a fourth separating box body, and communicated with a second settlement separating box body, and the top part of the helical pipe is communicated with the top part of a fourth settlement separating box body by a middle pipe; the outlet and the middle part of the bottom part of the side wall of the fourth settlement separating box body, which corresponds to the inlet, is provided with horizontal drain pipes and a horizontal oil discharge pipe respectively, and the other end of the horizontal oil discharge pipe penetrates the middle part of a third settlement separating box body; an upper horizontal pipe is communicated with a first helical pipe, the other outlet of the first helical pipe is connected with the inner part of the third settlement separating box body, and the bottom parts and the side walls of the top parts of the first and the third settlement separating box bodies are connected by pipes; the two horizontal drain pipes are provided with a water outlet pipe and an oil outlet pipe respectively.