The hydrogen measurement system can be used to accurately measure the hydrogen content in nitrogen carrier gas. The measurement principle is as follows: Collect the hydrogen in the molten steel by circulating nitrogen carrier gas between the molten steel and the pneumatic unit, complete the measurement when the hydrogen concentration in the molten steel is equal to that in the nitrogen carrier gas, and display the hydrogen content on the panel of the hydrogen measurement instrument. The on-line hydrogen measurement system is a high-precision measurement instrument and must be operated in strict accordance with the relevant procedures in the field measurement, to ensure the success rate and accuracy of measurement.