Abstract: Discussed in the paper is the influence on cut-distortion and bur-height by a number of variables during cutting of rectagular steel tubes with flying sawer,including feeding point,cutting force, deformation-resistance of the t u be and chip removal, etc. The optimum cutting conditions are proposed. Tile said cut-distortion and bur-height can be tremendously reduced by means of setting base positions of the flying sawer pneumatic cylinder and saw arm and keeping the cutting-in and cutting-out points just as the top points, of the two opposite angles of the rectagular tube.