Structural stability for selenium and tellurium nanowires is studied by combining first-principles method and empirical approach. This is an interesting topic due to the fact that the Se and Te crystals are composed of triangular Se and Te chains and that the chain-chain interaction is relatively weak. Nanowires of small diameters (<30?) are studied by first-principles calculations. Meanwhile, an empirical method that considers only the interaction between chains is also proposed in order to study the nanowires of larger diameters. The nanowires with hexagonal cross section are more stable, though the hexagon is not always perfect in shape due to the limitation of chain number. This result agrees with the widely accepted stable structures of selenium and tellurium nanowires.