Microwave heating was utilized for low-temperature crystallization of amorphous Si (a-Si) films. Microwave heating lowered the annealing temperature and reduced the annealing time. By microwave heating the hydrogen in the amorphous films was diffused out long before the nucleation of polycrystalline Si (poly-Si). The combination of NiCl2 coating on a-Si and microwave heating greatly reduced crystallization temperature. The combination of metal-induced crystallization and microwave-induced crystallization might be a useful technique to develop high-quality poly-Si films at low- temperature.