The invention discloses a marine natural gas hydrate development environment monitoring system and method. On a seabed, with a development point as the center of a circle, three concentric circles which are a first monitoring circle, a second monitoring circle and a third monitoring circle are arranged from the inside to the outside, and an in-site monitor, a seabed submerged buoy monitor and a mooring buoy monitor are arranged. In a development environment, four dimensions of data of an atmosphere, a seabed, seawater and an underground are monitored at the same time, and underground sedimenttemperature pressure / soil mechanics monitoring, seabed deformation monitoring of a mining area, the monitoring of seabed submerged buoy / mooring buoy, ROV-based real-time observation and monitoring, mining products and environmental impact monitoring are related. Monitoring ways cover many subjects of marine geology, engineering geology, physical oceanography, marine chemistry, marine biology and the like. A comprehensive environmental impact assessment technical scheme with the integration of 'seabed sediment, submarine sedimentation, multiple parameters of a submarine boundary layer, longitudinal profile characteristics of seawater, surface seawater and atmosphere, and the production of gas, water and sand' in one body is formed.