By modifying and improving the argon fraction control system, on the one hand, it is conducive to the stability of the working conditions of the main tower. On the other hand, the control value is reduced on the basis of the stable argon fraction, which is equivalent to increasing the argon content in the argon fraction and reducing the fluctuation range of the argon fraction, which is conducive to the stability of the crude argon tower working conditions and the increase of the argon extraction rate.