The invention discloses an OIW (Oil in Water) online monitoring probe and an OIW online monitoring device adopting the same. The OIW online monitoring probe comprises a probe body, wherein the probe body comprises a fixed boss, a front connector and a rear connector; the first connector and the rear connector are arranged on the front and rear sides of the fixed boss; the front connector is internally provided with an optical channel which extends axially; the front end of the optical channel is provided with a signal detector; the rear end of the optical channel is provided with an optical probe; the rear connector is internally provided with a signal converter; the signal detector is electrically connected with the signal converter; the optical probe and the signal converter are electrically connected with an external controller; the front connector is provided with a sample pipe which radially penetrates through the probe body, and the sample pipe passes through the optical channel. The detection part disclosed by the invention is high in integration, compact in structure and small in size; the detection probe is directly arranged on a water tank or a pipeline, so that a function of efficiently monitoring the OIW online in real time is realized; and meanwhile, a pulse xenon lamp serves as an excitation light source, so that the light intensity is stable and durable.