Objective The aim of the study was to discuss the application of biological optimization and its difference from physical optimization in hypofractionated radiotherapy for breast cancer after conservative surgery. Methods This retrospective study enrolled 15 randomly chosen patients with left-sided breast cancer who received radiotherapy. The volumetric arc therapy (VMAT) technique was used to redesign treatment plans with physical functions (PF) group, biological-physical functions combined (BF + PF and PF + BF) groups, and biological functions (BF) group. The dosimetric differences based on the above four optimization methods were assessed by calculating and analyzing the corresponding dose-volume parameters.Results The target parameters of the four groups differed significantly (P < 0.05) except for the conformity index (CI). The tumor control probability (TCP) values in the BF and BF + PF groups were higher than those in the PF and PF + BF groups. Moreover, the dose-volume parameters of the ipsilateral lung in the BF group were less than those of three other groups, while the monitor unit (MU) in the BF group was approximately 16％ lower than those of the PF and PF + BF groups. Conclusion Biological functions were useful to increase the equivalent uniform dose (EUD) and TCP values of the target, decrease the dose-volume parameters of the organs-at-risk (OARs), and improve treatment efficiency.