The invention discloses a reservoir hydro-fluctuation belt greenhouse gas monitoring system and a monitoring method and relates to the technical field of greenhouse gas monitoring. The monitoring system comprises a power supply, a cable, drought period greenhouse gas monitoring devices and a wet season greenhouse gas monitoring device, wherein the power supply is arranged on a platform above a highest water level line on a reservoir bank; the drought period greenhouse gas monitoring devices are half buried in a hydro-fluctuation belt between the highest water level line and a lowest water level line of a reservoir and are distributed in equal distances and are connected with the power supply together with the wet season greenhouse gas monitoring device on a water-air interface through cables. The reservoir hydro-fluctuation belt greenhouse gas monitoring system and the monitoring method disclosed by the invention are simple in arrangement and high in monitoring precision, greenhouse gas discharge situations of a reservoir hydro-fluctuation belt can be monitored at fixed points in real time in a guardless manner for a long time, monitoring data can be transmitted back in real time,the system can be mounted at any reservoir hydro-fluctuation belt, other monitoring equipment can be also carried in a position of a greenhouse gas monitoring device, and multi-angle fixed-point monitoring data acquisition is achieved.