Abstract: Nitrogen in the steel can either improve or weaken the performance, as well as reduce product. In the flow of producing steel, it is of paramount importance to adopt some measures to restrain or promote nitrogen dissolution in controlling the nitrogen content in the final product. The dissolution of nitrogen into molten iron in 1873 K has been measured by ¹⁵N-¹⁴N isotope exchange technology and online mass spectrometer. The results show that 600−800 mL·min⁻¹ of gas flow rate removes the effect of gas transfer, and increasing the hydrogen content in shielding gas decreases the content of impurity element. A certain amount of C, Al or Si was added to the molten iron, and the three elements were inhibited from the nitrogen dissolution rate. Based on the values of the work and using the dissociation determining model, the reaction apparent rate constant, k_a, was built the relationship with the content of oxygen, sulfur, carbon, aluminum and silicon. The adsorption coefficients were calculated to be K_O=0.96, K_S=9.32, K_C=0.02, K_Al=0.51 and K_Si=1.16, respectively. The nitrogen dissolution reaction apparent rate constant in pure liquid iron is k_a=4.8×10⁻⁶ mol·m⁻²·s·Pa.