The mech. and heat properties of fully biodegradable elastomer PHA and PLA composites were studied. The effects of types and contents of coupling agents, mesh and contents of talc on mech. properties, MFR of PHA/PLA composites were studied. We found that when PHA:PLA = 70:30, the PHA/PLA composites are stiff, flexible and good heat resistant. With 1% ligand titanic acid ester coupling agent treat 20 parts of 3000 mesh Talc, we can get the best PHA/PLA/Talc ternary composites. The DSC results indicate that the PHA/PLA/talc ternary composite has the rapid crystallization temperature between 50-75°, the melt temperature is about 150°.