ObjectiveTo research the effect of chondroitin sulfate (CS) on the proliferation of myoblasts and the formation of myotube. MethodsThe myoblasts at passage 5 were used to prepare the cells suspension (1×108 cells/mL), and the experiment was divided into 4 groups based on CS concentration in the medium:group A (0 μg/mL), group B (50 μg/mL), group C (100 μg/mL), and group D (200 μg/mL). The cell morphology and myotube formation were observed by inverted microscope at 4, 5, and 8 days after treatment; MTT was used to detect the cell proliferation at 6 days, and the number of myotube was calculated by HE staining at 8 days. ResultsCells showed spindle shape after adherent, with ovoid nuclei and dense cytoplasm under inverted microscope. When the cell adherent rate was 90%, cells arranged in whorls swirled and showed long fusiform adherent growth; and then nuclei fusion resulted in formation of multincleated myotubes. At 8 days, most myoblasts fused to form myotube in group A, but less myotube was observed in groups B and C, and the least myotube in group D. The absorbance (A) values of groups A, B, C, and D were 0.045 2±0.004 4, 0.540 4±0.096 7, 0.660 9±0.143 4, and 1.069 0±0.039 0 respectively, showing significant difference between other groups (P<0.05) except between groups B and C P>0.05). HE staining observation showed that most myoblasts fused to form myotube in group A, but less myotube in groups B and C, and the least myotube in group D. The number of myotube of groups A, B, C, and D were 222.01±30.02, 193.13±42.46, 170.26±11.96, and 136.88±16.78 respectively, showing no significant difference among groups (F=1.658, P=0.252). ConclusionCS can significantly promote the proliferation of myoblast, the promotion is the biggest when CS concentration is 200 μg/mL.