The present invention relates to a tri wavelength interference modulator (TWIM) and a method of tri wavelength interference modulation. The tri wavelength interference modulator includes: a stationary substrate with a bottom electrode plate formed on top of the stationary substrate; a first electrode plate comprising a first suspended beam suspended in parallel above the stationary substrate and a first connection electrically connected onto the stationary substrate; and a second electrode plate comprising a second suspended beam suspended in parallel above the first electrode plate and a second connection electrically connected onto the stationary substrate. The inference modulator and the method for inference modulation are suitable to projection system.