Manhole cover monitoring alarm system

The utility model discloses a manhole cover monitoring alarm system which includes a manhole cover body. The lower surface of the manhole cover body is provided with a drive plate and a control box; a mercury switch device is arranged on the drive plate; the mercury switch device is internally provided with a positive and negative contact claw and a mercury moving ball, wherein the mercury moving ball can move inside the mercury switch device and can contact or be electrically separated from the positive and negative contact claw; the positive and negative contact claw is connected with the control box through a wire; one end part of the drive plate is hinged with a connecting position of the lower surface of the manhole cover body; and the other end part of the drive plate is aligned with an outer circular edge of the manhole cover body. The manhole cover monitoring alarm system is novel in structure, skillful in design, and fast in testing and feedback speed, and can quite conveniently and quickly realize the manhole cover anti-theft effect. The manhole cover is provided with the drive plate with the mercury switch device; and when the manhole cover is moved, the mercury switch device immediately switches from the closed state to the cutting-off state, and the control box detects the state switching information and then transmits the state switching information to the monitoring center or the alarm device.