·A combined electrochemical probe assembled with 5 electrode collars of the same material is adopted and effectively reduces the effect of soil IR drop when measuring the corrosion current density; the connection method of counter electrode (CE), working electrode (WE) and reference electrode (RE) is represented by (CE-WE-RE), and the connection method of combined electrochemical probe is represented by (1-5，2-4，3). The area of working electrode (WE) and reference electrode (RE) is 5cm2;

·With four-electrode probe and a relatively low measuring voltage, the soil resistivity can be accurately measured, and the readout difficulty brought by high voltage measurement and physicochemical performance damage caused by soil electrolysis can be avoided;

·Standard platinum electrode and copper sulphate electrode are used to measure the soil oxidation-reduction potential;

·High-precision temperature measurer is fixed on the PTFE insulating rod of probe to measure soil temperature;

·Preformed hole method does little damage to the original soil structure and no excavation is required;

·Tapered design of front end is adopted to ensure good contact between probe and soil;

·Probe can be reused by polishing.