A biodegradable citric acid-based polyester (PEGCA) was synthesized by direct copolycondensation. The full biodegradable blends of PLA and PEGCA with different reaction degrees were made by using a torque rheometer. The tensile, impact and flexural properties were investigated and the morphologies of blends were assessed by scanning electron microscopy. The result shows that the PEGCA effectively improves the toughness of the blends. The elongation at break of the blends reaches 316% and the impact strength is also increased by 7 times. The tensile properties of PEGCA/PLA blends differ under different strain rate. The higher the strain rate is, the higher the tensile strength and the lower the elongation at break becomes. The dispersion of PEGCA with different reaction degrees in PLA affects the mechanical properties of the blends. The reaction degree of PEGCA affects the dispersion of PEGCA in PLA matrix. The PEGCA with low reaction degree shows relatively small dispersed phases in PLA matrix and its blend shows a better toughness and drawability under high strain rate.