To understand the effect of pyrocarbon (PyC) on the morphology stability of SiC nanowires at high temperatures (1800-2100 degrees C), a PyC layer was prepared to wrap the 3C-SiC nanowire by chemical vapor deposition. The results showed that the existence and thickness of PyC layer played a crucial role in stabilizing the structures and morphology of SiC nanowires. The SiC nanowires without PyC layer transformed to platelet-shaped structures above 1800 degrees C. The SiC nanowires with a similar to 1.5m PyC layer could keep their structures and morphology at 2100 degrees C, while the SiC nanowires with a similar to 1m PyC layer could not maintain their microstructures at this temperature. The stability of SiC nanowires at high temperature might be related to the vapor phase nucleation, thermodynamics phase transformation and the stacking faults (SFs) expansion, which could be limited by the PyC layer. Therefore, preparing a protective PyC layer with an appropriate thickness might be a potential method to extend the practical applications of SiC nanowires at high temperatures.