Objective To investigate the effectiveness and safety of volumetric modulated arc therapy (VMAT) hypofractionated radiotherapy and intensity modulated conformal radiotherapy technique (IMRT) conventional fractionated radiotherapy after breast cancer radical operation.Methods Eighty-five patients with breast cancer modified radical operation admitted and treated in this hospital from March 1,2021 to De-cember 30,2021 were selected as the research subjects and divided into the VMAT group (n=41) and the IM-RT group (n=42) according to the random number table method.The VMAT group adopted the hypofrac-tionated radiotherapy,with the single fractionated dose of 2.9 Gy/frequency and radiotherapeutic total dose of 43.5 Gy/15 frequencies;the IMRT group adopted the IMRT conventional fractionated radiotherapy,with the single fractionated dose of 2.0 Gy/frequency and radiotherapeutic total dose of 50.0 Gy/25 frequencies.The planning target region V95,V110,conformity index,homogeneity index,treatment time,V5,V20,V30,average dose (Dmean) in the affected side lung,humeral head Dmean and heart V30,Dmean were compared between the two groups.Meanwhile,local recurrence,distant metastasis,disease-free survival and acute and chronic radiation injury were compared between the two groups.Results Compared with the IMRT group,V95 in the VMAT was higher,V110 and homogeneity index were lower,the treatment time was shorter,V5 in the affected lung,Dmean and Dmean in the affected humeral head were lower,V30 in the affected lung was higher,heart V30 in the left side breast cancer was lower,heart Dmean in the right side breast cancer was lower,and the differences were statistically significant (P<0.05).All patients survived without local relapse.The distant metastasis rate and disease free survival rate had no statistical difference between the two groups (P>0.05).Follow up lasted for 12 months,the incidence rates of grade Ⅰ-Ⅱ acute radiodermatitis,radiation esophagitis,chronic radioder-matitis and radiation pneumonia had no statistical differences between the two groups (P>0.05).The inci-dence rate of grade Ⅰ-Ⅱ shoulder dysfunction in the VMAT group was lower than that in the IMRT group with statistical difference (P<0.05).No grade Ⅱ and above acute and chronic radiation injury in the two groups occurred.Conclusion VMAT hypofractionated radiotherapy after breast cancer radical operation is safe and effective.