The energy band structures of AnSn3 (An=Th, U, Np, and Pu) are investigated by using arelativistic linear augmented plane wave method with the exchange-correlation potential in thelocal density approximation. The energy bands near the Fermi level are mainly caused by thehybridization between the 5f and Sn 5p electrons of the actinides. The similarity of the Fermi surfacestructures in the AnSn3 compounds can be understood by using the change in the electron numbersinside the Fermi surfaces based on the rigid-band picture. The theoretical angular dependence ofthe de Haas-van Alphen frequencies in ThSn3 has been investigated.