Objective To evaluate the role and efficacy of scanning acoustic microscopy (microscopic ultrasound) in the treatment of calcified atresia root canal in elderly patients. Methods A total of 264 calcified root canals from 159 elderly patients admitted in the Department of Oral Medicine of our hospital from October 2016 to April 2018 were subjected into this study. They were divided into experimental (n=95,2 calcified root canals) and control groups (n=64,2 calcified root canals) according to their own wills. In the experimental group, the calcified root canals were treated with microscopy combined with ultrasound technology, while for the control group, manual C file and hole drilling were used for probing and dredging of calcified root canals. The patients of both groups were prepared with nickel-titanium root canal, filled with hot gum root, and treated with root canal therapy. The dredging situation after treatment was compared between the 2 groups. SPSS statistics 23.0 was used for statistical analysis. Student′s t test or Chi-square test was employed for comparison of different data types. Results The success rate of root canal dredging was 86.18%(131/152) in the experimental group and 54.46%(61/112) in the control group. Compared with the control group, the dredging rates of different tooth positions and different calcified root canals were significantly higher, while the dredging time was shorter obviously in the experimental group, both with significant differences (P<0.05). In the control group, 51 cases of undredged teeth were further treated by micro-ultrasonic technique, and finally 39 cases were dredged, with a dredging rate of 76.5%. Conclusion Micro-ultrasonic technique is quite effective in probing and dredging the calcified root canals in the elderly, and it also improves the success rate of the treatment.