The design of new magnetic material has become a hot area of research due to the potential applications of such compounds in new storage and information-processing technologies [1]. Coordination complexes built up of transition metal and rare-earth ions have recently attracted much attention in the field of molecular magnetism. Knowledge of the nature of these interactions is necessary for effective creation of new magnetic materials with interesting properties. Recently, the synthesis, structures and magnetochemistry of new series tetranuclear compounds [Fe3Ln(µ3-O)2(CCl3COO)8(H2O)(THF)3]THFC7H16 (Ln3+ = Sm3+ , Gd3+ , Dy3+, Ho3+ , Lu3+) were described [2]. In this work the EPR investigation of these compounds is presented. The aim of this study is to obtain information about spin-spin interactions. We carried out the measurements of the temperature dependence of the EPR spectra at X- and Q-bands for this series. The analysis of the spectra was performed using simulations of EPR spectra. The EPR spectra for Fe3Ln were simulated in the model taking into account the single-ion anisotropy term DFe, dipole-dipole interaction, isotropic and anisotropic Fe-Ln exchange interactions. The analysis of the EPR spectra in the X-and Q-bands for the Fe,3Ln clusters allows us to assume that only dipole-dipole interactions are realized between gadolinium and iron ions and between holmium and iron ions. Weak exchange interaction between iron and dysprosium ions is manifested. Simulation of the EPR spectra was performed using Matlab toolbox 'EasySpin' [3].