Abstract: The calcium content for inclusion distortion and the formation condition of sulfuric calcium in calcium treatment were calculated by thermodynamics method. The maximum content of sulfur after LF treatment and the minimum content of calcium after calcium treatment were determined. The effect of temperature and amount of feeding calcium on the yield of calcium and the relation between the soft argon blowing time after calcium treatment and the loss of calcium and aluminum were investigated. Based on calculation and experimental data, the process of calcium treatment was optimized, and the mass fraction of sulfur in steel after LF treatment is no more than 0. 007%. For each heat, feeding 100-200 m calcium line and blowing soft argon for 25 minutes after calcium feeding, the percent of pass of inclusions in the cold heading steel can reach up to 92%.