Titanium-Zirconium-Molybdenum alloy and Lanthanum-doped Titanium-Zirconium-Molybdenum alloy were fabricated by powder metallurgy method. The effect of lanthanum in arc erosion of titanium-zirconium-molybdenum alloy was investigated by using SEM, arc erosion test system and analytical balance. Results show that lanthanum-doped Titanium-Zirconium-Molybdenum alloy has a higher strength, density and lower electrical resistivity compared to that of Titanium-Zirconium-Molybdenum alloy. The average of arc energy and the arc time decrease 17.9% and 20.9% respectively because doping lanthanum decreases the arc current by forming reverse current between the contacts. The mass loss decreases 32.5% and erosion area reduces 32.6%. The lanthanum in the cathode has a good ability of electron emission.