Abstract: The process test of nitrogen alloying by 80t LF gas injection was made in CISC based on theoretical analysis of thermodynamics and dynamics. The technological measures of reasonable control on steel composition (sulfur, oxygen content), nitrogen flow and nitrogen blowing time were proposed. The results showed that，the treatment of feeding 36kg aluminium wire per heat before LF for precipitation deoxidation was conducive to nitrogen content increasing quickly. The higher the molten steel temperature was before large blowing, the better the nitrogen absorption effect was. The nitrogen absorption rate was stabled over 7×10^-6/min when molten steel temperature was over 1580 ℃. In order to satisfy w（N）≤200×10^-6, the time of nitrogen alloying by LF gas injection should not exceed 60 min. The yield strength and tensile strength of steel were increased, and the elongation was decreased slightly, but all of these met the national standard.

Key words: Ladle furnace，Nitrogen，Alloying，Test.