New techniques of ultrasonic welding and seam sealing have been developed instead of conventional sewing method to improve the performance of seam part of outdoor. The effects of the welding speed, seam sealing speed and washing cycle on the physical properties of seamed fabrics were investigated in this paper. The tenacity of seamed fabrics by welding after seam sealing process is about 70% of the tenacity of the seamed fabrics by conventional sewing after seam sealing process. The increase in speed of welding and seam sealing causes decrease in tenacity of seamed fabrics. The hydrostatic resistance and water vapor transport phenomena of welded fabrics are also discussed. The washing process affects the properties of seamed fabrics very slightly.