Aiming at the problems of cover loss, displacement, pipeline overflow, inner harmful gas accumulation and the other safety hazards associated with various municipal pipeline manholes in the construction of smart cities, a smart manhole monitoring system with the functions of information management, intelligent monitoring and precise scheduling is explored. This system can promptly and quickly handle the problems and improve the urban management efficiency. The smart manhole monitoring system mainly includes the manhole cover monitoring, water level monitoring, environmental temperature and humidity, flow monitoring, combustible/harmful gas monitoring, water quality detection and video monitoring, etc. The monitoring category is selected according to the characters and demands of manhole. The warning is issued when the limit is exceeded, and the alarm information is promptly sent to the platform or the mobile phone APP of the relevant operation and maintenance personnel. The real-time control and harm treatment of the whole process of the manhole with "one map" can be realized so as to achieve the comprehensive control and intelligent supervision.