The invention relates to a device and a method for monitoring vault settlement in tunnel construction. A monitoring device part mainly comprises an inclination measuring sensor, an inclination measuring pipe and a monitor, wherein the inclination measuring sensor is arranged in the inclination measuring pipe and is connected with the monitor by an electric wire. The principle of the monitoring method is that the deformation of the inclination measuring pipe is caused by the vault settlement, the inclination of the inclination measuring sensor can be further caused, the inclination change is converted into resistance change, and then the resistance change is converted into a voltage signal by an alternating current resistance bridge. The inclination amount of each sensor can be calculated,further the deformation amount of each section (1m) of the inclinometer pipe can be acquired, and then the deflection deformation of the whole section of the inclinometer pipe can be calculated according to an overlapping method, namely the total arch crown settlement displacement of the section. By using the device, the whole arch crown settlement process can be monitored before and after tunnelface excavation, the construction process is guided, and the construction safety is guaranteed.