Abstract: Monocrystalline dislocation-free silicon is grown by FZ in pure hydrogen atmosphere. Defects including microdefects can not be observed in as-grown monocrystalline dislocation-free silicon afteretching. But hydrogen induced defects and microdefects in FZ(H) Si will be always observed as FZ(H) Si rod after annealing. In order to remove the hydrogen induced defects and microdefects, the as-grown FZ(H) Si rod had to cut into the wafer which thickness is less than 1mm or NTD FZ(H) Si wafer is treatmented at the 940℃/0.5h. The qualified ratio was greater than 80% in the application of msnufacturing thyristors.