Abstract: Objective: To investigate the normal development of mandibular condylar cartilage in the mice, and to clarify the change of RUNX expression and its meaning. Methods: Mandibular condyle of Balb/c mice were fixed from embryonic day 14.5 (E14.5) through Postnatal day 7.5(P7.5). Samples were cut at the sagittal plane. The histomorphology were examined using Hematoxylin-eosin staining(HE). The RUNX protein levels and distribution were detected using immunohistochemistry (IHC). Results: The mesenchymal cell aggregation began at E14.5, followed by the appearance of full-layer differentiated chondrocytes. The condylar morphology developed from semicircular into flat form. IHC showed the expressions of RUNX1, 2 focused in the proliferation, prechondrocyte and part of the hypertrophic layer, while the RUNX3 mainly expressed in the prechondrocyte and hypertrophic layer. The RUNX1, 2 expressions, both in condyles’ anterior (ant) and posterior (post) segments, were relatively higher in the prechondrocyte layer than the hypertrophic layer. The expression level of all RUNX presented as bimodal curve. Conclusion: The anterior (ant) and posterior (post) segment of condyle remained in premature stage, which suggested its remodeling potential. RUNX1 cooperated with RUNX2 in mediating the early stage of chondrogenesis. RUNX3 played an important role in chondrocyte maturation.