We have studied the electronic structure of M@C28(M=Ti,Zr,Hf) endohedral complexes with ab initio method in B3-LYP effective core potential model and density functional theory.The computations were carried out for the geometry optimizations,which determined the structure constants of atoms in ground states,and the analysis of natural bond orbital.The interaction of Ti atom and C28 cluster was very different from that of Zr (or Hf) atom and C28 cluster. It occurred on the atomic configuration,the bonding character and the distribution of electronic states etc.According to the estimation of binding energy,three complexes could exist stably,and Zr@C28 and Hf@C28 were more stable than Ti@C28.The results have been analyzed and discussed,also compared with those in the literatare.