Abstract: The paper studies the magnetic focusing electron gun of CRT used in a new 48-inch rear color projection TV. The dual-focusing system in electron gun is developed, which is composed of electrostatic pre-focusing and electromagnetic focusing lens. As a result, on the green YAG phosphor screen, beam spot is 0.065 mm-0.080mm only at cathode currents of o.5 mA-1.0 mA respectively.