The invention provides an experimental device for simulating internal corrosion of pipelines. The experimental device comprises a corrosion experimental box, a temperature control box, a water circulating system, an oil circulating system, an electrochemical workstation and a computer. An experimental pipeline is arranged in the corrosion experimental box and is a double-layer pipeline, sample tables are arranged on the wall surfaces of the experimental pipeline, and samples are in smooth transition with the inner wall of the experimental pipeline. The experimental device has the advantages that oil products can be heated by water in an outer pipeline and can be uniformly heated, heat-insulation partition plates are arranged between the outer pipeline and an inner pipeline, and accordingly the experimental device can be used for simulating conditions of internal top corrosion of the pipelines, corrosion of pipe walls in the pipelines and internal flow corrosion of pipes due to fluid with various corrosive media under the normal pressure at different temperatures; corrosion conditions of the samples can be monitored in real time, the experimental device is high in automation and convenient to assemble and detach, and data are convenient to acquire.