The loss and volume of magnetic components in resonant DC-DC converters account for nearly 50%, which seriously restricts the improvement of power density in high-frequency converters. The magnetic integration technology can reduce the loss and volume of magnetic components, so it has been widely studied and applied. However, the traditional magnetic loss measurement methods cannot accurately and conveniently measure and evaluate the magnetic core loss of magnetic components in integrated resonant inductors and transformers, causing difficulties in the optimization of magnetic core loss. In this paper, the magnetic flux distribution in integrated magnetic components is analyzed, and a method is proposed to obtain the magnetic core loss of integrated magnetic components by testing the difference in losses before and after adding auxiliary integrated magnetic components in parallel in a resonant topology. At the same time, a parameter design method for auxiliary magnetic components is also put forward. This method can accurately and conveniently measure the magnetic core loss of integrated magnetic components under actual circuit conditions. Simulation and experimental results verified the effectiveness of the proposed magnetic loss measurement method for integrated magnetic components.