The geometric structures of the MnxSny (x=2,3,4; y=18,24,30) clusters are studied using the density functional theory method. The geometric optimization shows that the favourite structures of MnxSn6x+6 (x=2,3,4) are D3d single-cage structures which encapsulate Mn atoms, i.e. Mn2Sn18, Mn3Sn24 and Mn4Sn30.However the favourite structures of MnxSn6x+12 (x=2,3) are two-cage structures, i.e. MnSn12-MnSn12 and MnSn12-Mn2Sn18.Thus, it is promising to form new one-dimensional nonawires of MnxSny heterostructures by controlling the number of Mn atoms.