We have studied the formation process of carbon nanotube-silicon nanowire compound structures by using empirical molecular dynamics method and their thermal stability by empolying Lindemann index. Our results show that, in some cases, liquid Si encapsulated in C（13,0） and C（14,0） carbon nanotubes can crystallize into nanowires composed of linked Si16 and Si20 fullence cages, respectively. The Si nanowire inside the carbon nanotube has higher melting temperature then the Si nanowire in free space. By calculating interaction potential energy between SiNW clusters and carbon nanotubes with different diameters, we have found that the radial stress on Si20NW induced by the carbon nanotube can increase melting temperature of Si20NW. For Si20NW under free boundary condition, this radial stress can be released by the deformation of Si20NW which results in decrease of the melting temperature of Si20NW cluster.