The influence of the thermal properties of thermoplastic soya spent powder (TSSP) blends of high-density polyethylene (HDPE) at various compositions was investigated. The difference of thermal properties the blends with and without polyethylene-grafted-maleic anhydride (PE-g-MA) were investigated too. The compatibilizing efficiency of copolymers containing glycerol plasticized soya spent powder (SSP) were prepared by using heated two roll mills. Besides that, for the composition without compatibilizer TSSP was blended with HDPE by using twin screw extruder at 180^oC. Thermogravimetric analysis (TGA) reveals that the thermal decomposition temperature reduced with the addition of TSSF. However, the thermal stability of the blends was improved by the incorporation of PE-g-MA. Crystallinity of the blends was significantly dropped with increasing TSSP content and further reduced with the presence of PE-g-MA