High-frequency transformers(HFTs) are the in-dispensable component in isolated high-power dc-dc converters which have been the basic building blocks for solid-state trans- formers. To ensure high efficiency, high power density and high reliability, careful selection, design, modeling and evaluation are necessary for the magnetic core of an HFT. However, due to the nonlinear characteristics and the complex physical mechanism, magnetic cores have always been regarded as the focus and diffi-culty. This paper systematically reviews magnetic core materials commonly used in HFTs, core loss modeling methods based on classical Steinmetz equation(SE), and advanced core loss mea-surement techniques. Pros and cons for the magnetic materials, modeling and measurement methods are comprehensively ana- lyzed and summarized to provide a sufficient application insight.