Presence of liquid-liquid structure transition has been observed in Bi-20.5Te at 642 ℃ by measuring its electric resistivity with temperature increase. Through analyzing the atomic bonding mechanism of Bi-Te alloy melt with different compositions at different temperatures

it was concluded that the structure transition is arising from change in atomic cluster in the melt. The solidification curves of the alloy before （600 ℃） and after （700 ℃） structure transition has been mapped and its microstructure has been observed. The results show that compared with melt before structure transition at holding treatment

the alloy after structure transition holding at 700 ℃ needs higher undercooling degree and releases sharper latent heat during solidification

and possesses finer solidification microstructure

which is attributed to the debonding of Bi-Bi cluster and Bi-Te cluster in the melt structure

leading to uniform distribution of the melt to influence the atom diffusion during solidification

further to influence the solidification behavior and structure.