[Objective] To compare the clinical effect of minimally invasive precision bone grafting and traditional open bone grafting in the treatment of delayed union and nonunion. [Methods] Between May 2013 and March 2018,30 patients with delayed union and nonunion were included.15 patients underwent minimally invasive precision bone grafting, and the control group was treated with traditional open bone grafting, replacement or increasing internal fixation. The incision length,blood loss,operation time,postoperative complications ,hospital costs, bone healing and limb function were compared between the two groups. [Results] Minimally invasive group: The incision length was (1.38±0.28)cm, blood loss was (17.80±5.31)mL, operation time was（21.60±5.49）min, hospital costs was（5000±784.67）yuan,the incision healed smoothly, No serious complications. Routine treatment group:The incision length was （12.66±6.25）cm, operation time was （69.07±11.20）min, blood loss was （385.33±125.69）mL, hospital costs was（24546.67±3915.15）yuan,Two cases of wound infection,poor healing appeared, 1 case of deep vein thrombosis appeared.There were significant differences between 2 groups respectively (P＜0.05).There were no significant differences in bone healing rate and limb function excellent rate(P＞0.05). [Conclusion] Minimally invasive precision bone grafting and traditional open bone grafting can get satisfactory clinical results in the treatment of delayed bone healing and nonunion. However, minimally invasive precision bone grafting has the advantages of small surgical damage, simple operation, less complications, and economical and practical advantages.