[Objective] In order to improve the quality and efficiency of the soil and water conservation monitoring in the power transmission and transformation engineering, an online monitoring system integrating the function of data collection, storage and analysis was developed.[Methods] The influence meteorological factors (including rainfall, temperature, humidity, wind speed, wind direction and other factors) and soil moisture were chosen as the research objects in accordance with the technical requirements of the sensor, the traditional monitoring device, the newest testing technology, computer technology and communication technology, the key technologies of the online monitoring system was successfully developed.[Results] With the verification by field test, the data error rates were lower than 5%, which demonstrated the high accuracy and reliability. The operating state of the system was steady. The software user interface is simple and functional, which makes the data collection and analysis visual, real-time and accurate.[Conclusion] The developed key technologies of online monitoring system of the soil and water conservation monitoring in the power transmission and transformation engineering are stable and reliable. The system can satisfy the technology requirements and can be applied in practice.