Carbon nanotube cathodes(CNT cathodes) with a trench structure similar to gated structure of triode-type cathode were fabricated by a screen printing method using multi-walled carbon nanotubes. The effects of surface treatments on CNT cathodes were investigated for high efficiency field emission displays(FEDs). A liquid method easily removed the organic residue and protruded the CNTs. Field emission properties were measured by using a diode-type mode. The liquid method produced a turn-on field of $1.4V/{mu}m$. The emission current density was measured about $3.1mA/cm^{2}$ at the electric field of $3V/{mu}m$. The liquid method showed a high potential applicable to the surface treatment for triode-type FEDs.