Abstract: Objective: To determine the differences on the micro-tensile bond strength between different fresh and aged composite resin．Methods: Thirty composite resin specimens (Clearfil AP-X) were prepared． After being stored in distilled water at 37 ℃ for one month, composite surface was roughened with diamond bur and divided into three groups randomly, ten specimens in each group. In group A, ten specimens were used as substrate with adhesive to adhere fresh AP-X composite; fresh Z250 composite in group B; fresh TPH composite in group C. Specimens were then tested for the micro-tensile bond strength( μTBS) in a universal testing machine at a crosshead speed of 1 mm/min until failure．Results: μTBS of group B was the highest in the three groups. That of group C was second highest, and that of group A was the lowest. There were significant differences between three groups．Conclusions: In repairing aged composite resin, it is not necessary to use the same resin, which simplifies the clinical operation.