In Y2000, one factory introduced a second-hand 150 t LF furnace, with 25 MVA, 43 KA transformer, overload 20%. They chose to use UHP φ 350 electrodes. Although with 36 KA current limit, electrodes from home and abroad used to break and craft heating up was difficult. After carefully calculation and comparison, we suggest their technical department to use UHP φ 450 electrodes in March 2001.In October 2002, the plant declared: prepare to use UHP φ 400 electrodes instead. In October 2003, we were invited to a meeting aimed to analysis their LF furnace. During the meeting, we stated our advise:“By changing the UHPφ350 electrodes to UHP φ450 electrodes, the equipment could be matched and heat up and heat preservation purpose would be achieved.”In September 2004, our investigation found that the plant finally decided to change the electrode to UHP φ 450 after a comparative investigation.