. In order to improve the high temperature stability of casting mold, we carried out the RE Ion nitro-carbonizing technology test on the 4Cr5MoSiVl steel. This test was done by using high-power pulsed supply for the 4Cr5MoSiVl steel casting mold surface treatment under different temperatures, time period, atmospheric pressure, and RE contents. The optimization of these parameters makes the layer structure dense, toughness increased, specifically the surface hardness, wear resistance, high temperature oxidation resistance, and thermal fatigue properties of the treated layer significantly improved. A test with the use of this technology has been done for the 4Cr5MoSiVl steel automotive lamp aluminum casting mold. The mold service life of each mold time increased from 30,000 to 100,000. The experimental results show that by using 4%RE 520oC×2h, and 1.05KPa atmospheric pressure, the treated layer has optimal qualities, which can meet the requirements in practice.