Objective: To investigate the results of super-high molecular weight polylactic acid internal fixation system used to treat mandibular fractures. Methods: The fractures were produced bilaterallly at the mental foramen area in the mandibular body and fixed with super-high molecular weight polylactic acid internal fixation system on the left side and a stainless steel internal fixation system on the right side as control. Viviperception, macroscopic observation, microscopic observation, radiographic examination, molecular weight test, SEM, and biomechanical assay were performed. Results: The mechanical strength of super-high molecular weight polylactic acid fell slowly in the first month and rapidly thereafter. Super-high molecular weight polylactic acid had largely degraded in 6 months postoperatively and had degraded entirely at 12 months post-operation. There was some mild and transient tissue reaction around super-high molecular weight polylactic acid. Some new bone deposited on the surface of super-high molecular weight polylactic acid and between the bone and super-high molecular weight polylactic acid. The stainless steel internal fixation system can provoke serious inflammatory reaction. Super-high molecular weight polylactic acid internal fixation system had a similar internal fixation effect as the stainless steel internal fixation, and was better than the stainless steel internal fixation in terms of biodegradation and biocompatibility. Conclusion: Super-high molecular weight polylactic acid internal fixation system is suitable for internal fixation of mandibular fractures.