A novel tungsten cathode material with six percents of nanoscale ThO2 used in arc plasma has been fabricated by Hot Pressing(HP) sintering. A comparative study with the cathode of two percent nano ThO2 has been made on microstructure, starting characteristics and mechanical behavior. The results show that the microstructure, consisting of tungsten matrix with homogeneous dopants of ThO2 less than 200nm, is the same as the W 2%ThO2 cathode. The arc starting field for this cathode is lower than that of the reference cathode. Its work function is also correspondingly reduced. The differences between their mechanical behavior are not much.