Objecitve To evaluate effect of ultrasound-guided close reduction and modified mini external fixation for pediatric unstable distal radial fracture. Method Between March 2017 and December 2020, 56 children with unstable distal radial fractures were treated. There were 33 males and 23 females.The average age was (6.63±3.19) years [range 1 to 11 years]. There were 16 cases at left side and 40 case at right side. The average weight was (26.38±10.92) Kg [range 12 to 57 Kg], and the average body mass index was (21.91±2.09) Kg/m2 [range 17.3-32.8 Kg/m2].The average trauma time was (9.92±1.31) days [range 5 to 12 days]. All children were divided into two groups : 30 children in modified group were treated with ultrasound-guided close reduction and modified mini external fixation and 26 children in control group were treated with fluoroscopy-guided close reduction and traditional external fixation. Operation time, inpatient time, blood loss ,count of X-ray, time of bone healing, pain score after 24 hours, Gartland-Werley function score at last followup were recorded. Result There were significent difference about operation time, inpatient time, blood loss ,count of X-ray and pain score after 24 hours between two groups (P<0.01),but there were no significent difference about time of bone healing and Gartland-Werley function score at last followup (P>0.05).There was one clild with infection in modified group,and three children with infection,one with loosen of Scanz screw and two with repture of musculi abductor pollicis longus in control group. Conclusion Ultrasound-guided close reduction and modified mini external fixation for pediatric unstable distal radial fracture, is safe,efficent and less radiation damage, and could be an alternative for traditional external fixation.