The mixed manganese carboxy-clusters have been attracting an intense interest during the last several years. There are many reasons for this, including their wide application as catalysts, as well as in study of photosynthetic processes and the perspective to improve the properties of SMM. In the present work, the synthesis and exchange interaction measurements in a new heteropolynuclear manganese cluster are described. The reaction of [Mn3O(C6H5COO)6(py)2(H2O)] with Ca(ClO4)2 in MeCN in the presence of 2hydoxymethylpyridine (H-HMP) forms the [Mn6Ca2(HMP)6(C6H5COO)6O3(H2O)10](ClO4)4 (1) complexes, with a very good yield. Its molecular structure comprises a hexa-manganese ring with a dimeric calcium complex threaded into the central cavity [1]. Considering the molecular formula, each manganese is assigned to the +3 oxidation state.In Figure 3, the dependence of Gauss function fG(H-H0) (black circles) and Lorentz function fL(H-H0) (open circles) versus (H-H0)2 in linearized coordinates are presented. The EPR spectrum of 1 consists of a large almost symmetrical line with the g-factor g = 1.993 and the width deltaHpp = 544.1 Oe. This line shows a hyperfine structure with the constant a = (90.4 ± 3.3), cm-1·104, due to the interaction between five 3d-electrons of the Mn2+ ion in the ground state and the 55Mn nucleus with the spin I = 5/2 (Figure 2). Based on the method of linear anamorphoses [2] (Figure 3), we demonstrate that the exchange field in 1 is He= (530 ±30) Oe. Supplementary, it was shown that the intensity of the EPR line at temperature T = 77 K is higher than at T = 296 K: (I77K)/(I296K) = 3.34, suggesting that 1 is a compound with an exchange interaction of ferromagnetic type in the ground state.