A vibration isolation system of mass flowmeter, includes upper horizontal section, vertical section, lower horizontal section, upper arc section between the upper horizontal section and vertical section, and lower arc section between the vertical section and lower horizontal section of U-shaped measuring tube. On the lower arc section there is vibration isolation block. It is characterized by full-length welding between the vibration isolation block's plane of the axis of U-shaped measuring tube and the lower arc section. The U-shaped measuring tube has an inertia center. The straight-line distance between the external welding point in the full weld of the lower arc section between the vibration isolation block mentioned and the measuring tube and the inertia center is equal to the straight-line distance between the internal welding point and the inertia center.