The present disclosure provides a high-frequency magnetoimpedance testing apparatus and method. A testing platform in the apparatus is arranged within a Helmholtz coil and connected to a modulating electric current source and a high-frequency impedance analyzer, respectively; the Helmholtz coil is connected to a DC power source; a processor is connected to the high-frequency impedance analyzer and the DC power source separately; the testing platform includes a first double-sided copper-clad plate, and mode transition switches and connection terminals that are arranged on the first double-sided copper-clad plate; one end of the first double-sided copper-clad plate is connected to the high-frequency impedance analyzer, while the other end of the same is connected to a load; the mode transition switches are connected to the modulating electric current source. The present disclosure can realize in-situ current modulation of metallic fibers and high-frequency magnetoimpedance testing, and improve the testing accuracy.