The viscosity-temperature curve of Bi melt showed that the viscosity values deceased with the increase of temperature. However, the discontinuous changing pattern took place on the viscosity curve. Viscosity of Bi melt can be divided into three parts as high temperature zone, moderate temperature zone and low temperature zone according to its change rate with temperature. The temperature ranges of the abnormal viscosity change were about 400~430°C and 610~640°C. With the DSC analysis, the abnormal phenomenon was explored from the microscopic structure viewpoint. It was assumed that the change from inhomogeneous atom configuration to homogeneous one led to the discontinuous variation, which is related to the bond transformation with the increase of temperature in melt Bi.