Objective To precisely treat compl icated calcaneal fracture by 3D simulation through computer aid designed operation. Methods From November 2007 to March 2008, 38 patients of calcaneal fracture were treated. There were 29 males and 9 females aged 14-69 years old (average 29.8 years old). According to Sanders classification, there were 4 patients oftype I, 14 of type II, 12 of type III, and 8 of type IV. The time between injury and surgery was 3 hours to 5 days. The CT images of calcaneal fracture of 38 patients were put into computer for 3D reconstruction, then the Bouml;hler angles were measured and bone grafting angles were designed. According to the angle surveyed by the computer, the individual-oriented operation program was made, and then the operation was done under C-arm X-ray machine. Results The preoperative Bouml;hler angel was (34.58 ± 4.38)° in the normal side and (8.33 ± 12.62)° in the injured side, indicating there was significant difference (P lt; 0.05). During the process of the poking reduction by 3D simulation, when the bone rotating angle was (28.84 ± 6.51)°, the Bouml;hler angel was restored to (32.86 ± 1.72)°, indicating there was no significant difference when compared with the normal side before operation (P gt; 0.05), and significant difference compared with the injured side before operation (P lt; 0.05). Twenty-eight patients were followed up for 12-22 months (average 18 months). The Bouml;hler angel was restored to (32.41 ± 1.42)° 1 year after operation. According to the foot function scoring system made by American Ankle Surgery Association, 16 cases were graded as excellent, 10 as good, 1 as fair, 1 as poor, and the excellent and good rate was 92.9%. Conclusion Computer aid designed operation of compl icated calcaneal fracture by 3D simulation technique can restore the Bouml;hler angel and subtalar joint precisely. It is aneffective supplementary treatment method for calcaneal fracture.