Abstract: Operational principle of the flying saw is analyzed.A supporting device is designed，and mounted between the flying sawing machine and the rapid pull-out machine to solve the trouble that the minimum length cut by the flying saw in the line is restrained due to the specific distance between the sawing machine and the run-out roller frame of the rapid pull-out machine.Elaborated here in the paper are the main aspects of the said supporting device，including the operational principle，operation procedures，structural features，and the hydraulic and electric control systems.Thanks to the supporting device，in-line minimum short piece cutting，and in-line crop-shortening are realized.As a result，both production capacity and productivity of the operation line are increased，and accordingly，the yield is increased.