The invention discloses a testing device and method for simulating oil spillage of an underwater pipeline and belongs to the technical field of the safety of the underwater pipeline. The device comprises a testing water tank, a fluorescent sensor, a hydrophone, an acoustic detection device, a temperature sensor A, an oiling pressure sensor, an oiling temperature sensor, an oiling flow-meter, a return oil flow-meter, an oil pipeline pulsation damper, a gear oil pump, a control valve and a control cabinet, wherein the control cabinet is electrically connected with an oil nozzle, the fluorescentsensor, the hydrophone, an acoustic emission transducer, an acoustic receiving transducer, the temperature sensor A, the oiling pressure sensor, the oiling temperature sensor, the oiling flow-meter, the return oil flow-meter, an oil pipeline pressure sensor, the oil pipeline pulsation damper, the gear oil pump, a stirrer, a heater and the control valve, respectively. According to the testing device and method for simulating the oil spillage of the underwater pipeline, various changed oiling conditions and the oil spillage situation of the underwater pipeline can be simulated, an experimental process is monitored in real time through the multiple sensors, and the oil spillage situation of the underwater pipeline is simulated more truly.