In this Letter, we propose a method of fabricating linear variable filters by ion beam etching with masking mechanisms. A triangle-shaped mask is designed and set between the ion source and sample. During the ion etching, the sample is moved back and forth repeatedly with a constant velocity for the purpose of obtaining the linearly varied thickness of the cavity. Combined with ion beam assistant thermal oxidative electron beam evaporation deposition technology, we finish the fabrication of linear variable filters, whose filtering range is from 500 to 580 nm. The measured results indicate that the transmittance and bandwidth at the peak wavelength are around 40% and 3 nm.