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.