Objective: Osteoradionecrosis of jaws (ORNJ) is a severe complication of radiotherapy in head and neck cancer.However, no suitable experimental animal model exists to study the pathogenesis and treatment.The goals of this study were to establish a reproducible ORNJ animal model and to observe the existence of myofibroblast and the expression of some fibrosis-related molecules, which could be a proof of RIF (radio-induced fibrosis) mechanism in ORNJ.Methods: 16 rabbits were randomized into four groups: group 1 served as control, and left mandibular in group 2, 3 and 4 received iron irradiation at doses of 8.0Gy, 8.9Gy and 9.7Gy every two days and 5 times for total respectively, which approximated to 60Gy, 70Gy and 80Gy of the bioequivalent dose in head and neck cancer treatment.45 days after irradiation, the first two left mandibular molars were extracted in all groups.3 months later, rabbits were examined by clinical manifestation, histology observation, and micro CT scanning to select the most suitable model.Myofibroblast was detected by its phenotypic marker a-SMA, and TUNEL method was used to detect its status of apoptosis.TGF-b,CTGF, Col Ⅰ and Col Ⅲ expression were also measured by WB and RT-PCR.