Objective:To compare the efficacy of composite restoration in the treatment of three kinds of cracked teeth at 2 years after the operation. Methods:According to experimental method and types of crack,95 cracked maxillary first molars were divided into 3 groups. All the teeth were restored with a composite restoration and the curative effects of different kinds of cracked teeth were com-pared at 2 years after the operation. Results:With 2-year follow-up,the success rate of single cracked group was 86.1% while pen-etrating cracked group was 76.7% and mixed cracked group was 48.1%. Results showed that the curative effect of mixed crack was obviously lower than that of single crack after 2 years,mainly concerning pulp survival and restoration survival,but no significant difference was observed between penetrating crack and other crack. Conclusion: Prognosis of cracked tooth is closely related to the type of crack.