Accurate calculation of the alternating-current (AC) impedance of radio-frequency (RF) coils is essential for optimizing the performance of magnetic resonance logging probes. The flexible printed circuit board structure of the probe coil, characterized by a large disparity between thickness and lateral dimensions and its integration with magnetic core materials, makes it difficult to apply conventional finite element methods effectively. To address the low accuracy in electromagnetic parameter computation, a modeling approach based on the partial element equivalent circuit (PEEC) method was proposed by introducing magnetization strength as a key variable. Tetrahedral mesh discretization and vector basis functions were used to accurately model the irregular probe structure. An equivalent circuit model of the magnetic core was established, and the PEEC network of the coil-core composite structure was subsequently derived. Numerical simulations and experimental validations were conducted over the frequency range of 0.1 ~ 2?MHz. The results show that the calculation errors of AC resistance and reactance are less than 5.10 % and 3.24 %, respectively, and are consistent with measured values. Compared with Q3D simulation results, the resistance error was reduced by 30 %, confirming that the proposed model achieves high accuracy in simulating irregular coil-core composite structures and provides reliable support for electromagnetic modeling and performance evaluation of complex magnetic resonance logging probes.