The utility model relates to a testing arrangement is corroded at moisture loop top is applicable to the mechanism research of corroding simulation experiment and corrosion behavior in the moisture top under actual high temperature high pressure operating mode. The utility model discloses a heating cauldron, pipeline circulation system, heating heat preservation system, circulation condensation water tank refrigerating system, circulating pump, signal conduction path, external control box, flow state observation window, external gas supply system, three electrode systems, electrochemistry workstation and computer schedule. The inside actual ambient condition of pipeline, fluidic flow state in the pipeline, the velocity of flow, pressure, temperature etc. Can really be simulated to the device's advantage to real electrochemistry data are measured to the actual environment of simulation that can furthest. Utilize this equipment both can carry out the top to the sample and corrode normal position electrochemistry signal testing, also can utilize the weight -loss method to study the corrosion mechanism of pipeline steel. Consequently, this equipment has extremely important meaning to the moisture top corrosion mechanism research of pipeline steel.