The invention discloses an integrated electrolytic tank system and method for an in-situ electrochemical mass spectrum detection system. The system comprises a three-electrode electrolytic tank, an electrolyte replacement device and a built-in temperature control device. The three-electrode electrolytic tank is composed of an auxiliary electrode electrolytic tank, a research electrode electrolytic tank and a reference electrode electrolytic tank. The electrolyte replacement device is composed of a liquid storage tank, a waste liquid tank, a peristaltic pump and connecting pipes. The built-in temperature control device is composed of a built-in glass tube, a resistance wire, a thermocouple, a transformer and a relay. According to the system, smooth temperature control can be achieved; meanwhile, due to the built-in design, interference with sight can be avoided, and observation of an electrode and mass spectrum connection port will not be influenced; besides, electrolyte flow can be controlled by controlling switches of upper and lower electrolytic tank electrolyte ports, electrolyte replacement can be achieved through flowing of a certain quantity of electrolyte, and meanwhile circuit connection can be kept.