The invention provides a top-corrosion electrochemical testing device in high-temperature and high-pressure environments, belongs to the field of corrosive electrochemistry, and is suitable for top-corrosion simulation experiments and corrosion behavior mechanism research in high-temperature and high-pressure working conditions. The top-corrosion electrochemical testing device comprises a high-temperature and high-pressure reaction kettle, a heating and heat preservation system, a circulating condensate water tank refrigerating system, a three-electrode system, a signal conduction pathway, a control box, an external air supply system and a computer. The device has the advantages that actual high-temperature and high-pressure working conditions can be achieved; top-corrosion in-situ electrochemical signal testing can be carried out; and the method is of great significance on mechanism research on high-temperature and high-pressure top-corrosion behaviors and electrochemical reaction.