The invention relates to a parameter design method for a load electric reactor of a maximum metal condition (MMC) valve steady-state operation testing device. The parameter design method includes the following steps: carrying out equivalence on the steady-state operation testing device in a working state; determining an active power balance relation of a sinusoidal steady state equivalent circuit; determining a reactance value of the load electric reactor which meets the active power balance relation; determining a frequency doubling current according to reactive power exchange between an auxiliary valve and a trying valve; and determining the relation between the frequency doubling current and the reactance value of the load electric reactor. The parameter design method for the load electric reactor of the MMC valve steady-state operation testing device meets the active power balance relation of the steady-state operation testing device, and can restrict second harmonics of the current in a reasonable range.