The invention relates to an experimental detecting system and method for distribution of remaining oil in a fracture-cavity reservoir bed. The experimental detecting system comprises a constant-flux pump, a container containing formation water, a container containing compounded crude oil, a container containing a contrast agent, a four-way valve, a fracture-cavity reservoir bed flat model, a core holder, an X-ray tomoscan system and a data processing and imaging system, wherein the container containing formation water, the container containing the compounded crude oil and the container containing the contrast agent are connected with the three inlets of the four-way valve through a first pipeline, a second pipeline and a third pipeline respectively; the outlet of the four-way valve is connected with the injection opening of the core holder through a pumping pipeline; the output opening of the core holder is used for outputting a liquid; the liquid output from the output opening of the core holder is collected in a measuring cylinder. According to the experimental detecting system and method, the oil-water displacement process under a formation condition is simulated actually, and the percolation mechanism and the remaining oil distribution rule are similar to practical water injection in a mine, so that the detection conclusion has a guiding significance in mine application, and the problem that the water injection and oil displacement process cannot be visual is solved.