The invention relates to a shutdown state change and restart stress measurement device and method for an oil-water mixed transportation subsea pipeline. The device comprises an experiment pipeline unit, a rotating operation unit, and a temperature control unit. The experiment pipeline unit is used for simulating a shutdown and restart process of oil-water mixed transportation of a pipeline and employs an L-shaped combined pipeline. The rotating operation unit is used for rotating the L-shaped combined pipeline to uniformly mix oil and water in the pipe section. The temperature control unit isused for controlling the oil-water mixing temperature in the L-shaped combined pipeline, simulating a real use environment, researching an initial flow pattern change rule of oil-water mixed transportation outage under different temperature working conditions and performing restarting stress testing. According to the invention, the shutdown and restart characteristics of oil-water mixed transportation in the combined pipe under different water contents and different temperatures can be rapidly and conveniently measured.