One of the models for the carbon nanotube array with parallel grids is proposed. The actual electric field at the top of the carbon nanotubes and the field enhancement factor are calculated analytically with the image charge method and floated sphere model. The effects of the geometrical parameters of the device and the contact resistance on actual electric field, field enhancement factor at the top of carbon nanotubes, and the field emission current from the gated carbon nanotubes are investigated. The calculation results show that the carbon nanotube array has the best density for field emission when the intertube distance is twice the height of carbon nanotube. The actual electric field and the field emission current from gated carbon nanotube are greatly reduced by the contact resistance. When the contact resistance is larger than 800 kΩ, the emission current from carbon nanotube tends to be zero and the field emission properties are improved via modulating gate voltage.