Objective To study the effect of peroxisome proliferator-activated receptor δ (PPARδ) on myosin heavy chain (MHC) subtypes during myoblast differentiation.  Methods Primary myoblasts from newborn mice were isolated, control group, PPAR delta agonist group and PPAR delta antagonist group were set up. Cell samples were collected at 2, 4 and 6 days of cell differentiation in each group. Identification of cell differentiation in each group was made by MHC immunofluorescence; The expression levels of MHC subtypes were detected by Real-time PCR; Western blotting was used to detect the MHC protein expression levels in each group.   Results The expression of myotube and MHC protein in PPARδ agonist group were higher than that in control group and PPARδ antagonist group. By comparing the four MHC subtypes treated with PPARδ agonist, it was found that: after 2 days of differentiation, the up-regulation of MHCⅠ and MHCⅡa was significant; After 4 days of differentiation, the up-regulation of MHCⅠ, MHCⅡa and MHCⅡx was significant, and the up-regulation of MHCⅡa was the largest; After 6 days of differentiation, the up-regulation of MHCⅠ and MHCⅡa was significant, and the up-regulation of MHCⅡa was the largest.   Conclusion PPARδ promotes mouse myoblast differentiation and significantly upregulates MHCⅡa expression during differentiation.