Several kinds of nozzles were made by modifying the MJS(Murata jet spinner), in order to observe the mechanism of the air-jet spinning. They were 15 times bigger than those of MJS. Compressed air was supplied into them through the pipes which were stuck with an incline of several tens of degrees to the axis of the nozzle. The flow behavior of air and the configuration of the fibre strand in the nozzle were studied by observing the movement of the roving which were rotated in the modified nozzle. Of course the tension of the roving was controlled. By the way, sample yarns were spun under the several processing conditions which were varied by some spinning parameters. Some conclusions were obtained as follows. The number of revolutions of fibre strand per unit time should be increased in order to increase the output of the air-jet spun yarns. But it should be controlled in order to flow the fibres into the nozzle because the pressure flow arose. And it increased with increase of the air pressure.