The geometric and electronic properties of the three isomers for C72 and La2@C72 have been studied using the generalized gradient approximation in density functional theory (DFT). It is found that C72(D6d) which satisfies the isolated-pentagon rule is the most stable structure among the three isomers of C72, while La2@C72 (#10611) is the most stable structure and La2@C72 (D6d) is the most unstable structure among the three isomers of La2@C72. It is also found from the analysis of energy levels as well as the density of states that the stability change is due to the mixing of La atomic orbital with C atomic orbital in C72. From Milliken populations, we find that there are about three electrons transferring from the two encaged La atoms to C72 cage so the electronic configuration of La2@C72 (#10611) can be described as La3+2@C3-72. We also come to the conclusion from the net spins of La as well as of La2@C72 that the magnetic moments of La have been completely quenched so La2@C72 (#10611) shows no magnetism.