The present paper reports kinematic studies of the glass transition in glassy Se80-xTe20Sbx alloys using the differential scanning calorimetric technique. The glass transition temperature (T-g) is found to increase monotonically with the heating rate. T-g also increases with the increase of Sb concentration in ternary Se80-xTe20Sbx system. From the heating rate dependence of glass transition temperature, the activation energy (Delta E-t) for the relaxation time controlling the structural enthalpy, is calculated. The composition dependence of T-g and Delta E-t is discussed in terms of the structure of the Se-Te-Sb glassy system.