We make a systematic calculation on α-decay branching ratios to members of ground-state rotational band and to excited 0+ states of even–even nuclei by a simple barrier penetration approach. The branching ratios to the excited states of daughter nucleus are determined by the α-decay energy, the angular momentum of α-particle, and the excitation probability of the daughter nucleus. Our calculation covers isotopic chains from Hg to Fm in the mass regions 180