Abstract: Objective To study the obstruction at ureteropelvic junction（UPJ） in children and its treatment. Methods Clinical data about 29 children with obstruction at the UPJ admitted to our department from May 2005 to April 2012 were retrospectively analyzed,including pathological anatomy of UPJ,treatment modalities,postoperative complications and prognosis.Tissue samples were observed with H-E staining. Results Of the 29 patients,14 were diagnosed with stricture at the UPJ,6 were diagnosed with kinking,folding,and angulation at the UPJ,4 were diagnosed with compression of aberrant vessels,1 was diagnosed with torsion at the anastomotic stoma who underwent a second operation,1 was diagnosed with scar formation at the anatomotic stoma accompanying segmental stricture of the upper ureter,1 was diagnosed with transit hydronephrosis due to kidney stones,and 1 was diagnosed with ureteral epithelioid polyps.Of the 26 patients who underwent the Anderson-Hynes procedure,1 accepted fiber tissue dissection to release the UPJ,1 with secondary hydrophrosis had his kidney stone excreted,1 underwent partial resection of ureter and anastomosis of pelvic and ureter.Of the 29 patients,27 were cured with a successful rate of 93.10% and a perioperative complication rate of 37.93%（11/29）.The complications included urinary tract infection,urinary fistulae,anastomotic edema,hematuria,hypertension and ureter stricture.The complications influencing the therapeutic effect were urinary fistulae accompanying infection with Candida albicans and segmental stricture of the upper urinary tract,etc.Chronic mucosal inflammation,edema of lamina propria,proliferation of fiber connective tissue,disordered arrangement of muscles,and proliferation of muscle fibers,etc,were observed in the children with congenital obstruction at the UPJ. Conclusion Pathologic lesions at the UPJ in children include congenital stricture,kinking,folding,angulation,compression of aberrant vessels,and fiber adhesion of ureter,scar formation at the anastomotic stoma,torsion of anastomotic stoma,kidney stone,and fiber epithelioid polyps of ureter.The patients should be treated with different procedures according to their disease condition.Urinary fistulae,fungus infection and untreated stricture of ureter are the factors that will ultimately affect the therapeutic effect.