Semaphorin4D (Sema4D) belongs to Semaphorins family and is secreted and membrane-bound protein. Its function on angiogenesis and axon regeneration makes it an ideal therapeutic target for spinal cord injury (SCI). Here we examined Sema4D expression profile by real-time PCR and western blot and found Sema4D was upregulated after SCI. In vitro study showed Sema4D was not only expressed in oligodendrocytes but also in endothelial cells (ECs). Hypoxia can mimic Sema4D upregulation in both cell lines. Moreover, overexpression of Sema4D through lentivirus in ECs promoted tube formation. However, Sema4D overexpression in oligodendrocytes precursor cells (OPCs) inhibited neuron myelination in neuron-oligodendrocyte co-culture system. Therefore, Sema4D knockdown in OPCs was applied in SCI rats. The results indicated that Sema4D knockdown significantly promoted functional recovery with blood-brain barrier score. Taken together, our data suggest that specific Sema4D knockdown in oligodendrocytes without disturbing its angiogenesis effect can be a beneficial strategy for SCI treatment.