Poly Lactic Acid (PLA) is a biodegradable polymer. PLA can be prepared by two chemical reaction, ring opening or direct condensation polymer. In order to increase the biodegradability of polymer and to decrease its high cost, an effect have been made to blend with starch, due to the low cost of starch. This blending has an effect of fully biodegradable material. By contrast, few bends have poor mechanical properties. In this analyze, starch is blended with low level of MDI (Methylene Diphenyl Diisocyanate).As it could be a good coupling agent between starch & PLA. The emphasizing of this blend with MDI was to determine its mechanical &thermal properties. Scanning Electron Microscope (SEM) on the observation of blend was also performed. No significant difference in water absorption occurred between the blend with or without MDI. Results revealed that the strengthening of blends in the development of biodegradable plastics.