Objective: To investigate the safety of super-high molecular weight polylactic acid (SHM-PLA) on osteoblasts. Methods: The osteoblasts derived from neonatal rats were grown and maintained at steep SHM-PLA and normal culture medium. The viability and function of the osteoblasts were measured with Methylthiazole tetrazolium assay. Results: There was no significant difference of OD values between the experimental group and the control group (P > 0.05). SHM-PLA was not toxic to osteoblasts at week 1 and week 2, and the toxicity was 3% at day 3. Conclusion: SHM-PLA has no pathologic influence on osteoblasts, and SHM-PLA is feasible as an internal fixation material with cytologic security.