A linear annealing method for silicon wafer direct bonding was developed and applied for silicon-on-insulator (SOI) substrate fabrication. The new annealing method was similar to a conventional zone-melting system, except with no additional lower heating modules. The bonded interface, observed using an infrared camera and a transmission electron microscope, showed no gaseous defects. The bonding strength was high enough to separate the thermal oxide layer from the Si wafer surface, which was observed through the tensile test. The bond strength increased with increasing annealing temperature. The new annealing method was thought to be more effective compared with the conventional furnace annealing, as it offered low temperature and fast processing time without the decrease of bond strength.