The present invention discloses a radial pressure-variable wound core transformer loss test system and a test method thereof. The system mainly comprises a voltage regulator, a digital power analyzer, a wound core transformer test platform and a radial pressure applying device. The radial pressure applying device is fixed inside a transformer wound core of the wound core transformer test platform. In this way, the radial pressure applied on the wound core and diversified in direction and magnitude can be simulated based on the four support members of the radial pressure applying device and the four corners of the inner window of the transformer wound core. Therefore, the loss of the wound core can be tested under the effect of the radial pressure different in direction and magnitude, and loss parameters are measured. Furthermore, the core state can be evaluated and the core structure is optimized.