The invention discloses a large-size magnetic core high frequency magnetization characteristic measuring device and a selecting method for the number of turns of a magnetic core. A signal generator is used to provide excitation for a magnetic core to be measured through a power amplifier and an isolation bias unit. The waveform of an excitation signal is controlled by adjusting the output waveform of the signal generator, and at the same time the symmetry of the excitation signal and periodic magnetization is ensured through the isolation bias unit. When a platform is used for measuring, the size applicable for the magnetic core is determined by the output characteristic of the power amplifier. According to the applicable magnetic core selecting method provided by the invention, the magnetic core size which can be measured by the platform and the corresponding range of the number of turns are calculated according to the output characteristic of the power amplifier and the delivery parameters of the magnetic core; the measuring device satisfies the measurement requirement of a large-volume magnetic ring saturation hysteresis loop; and the pertinence and the efficiency of high-frequency magnetization characteristic measurement of the large-size magnetic core are improved.