In this study, observing the true length that the black polyester fiber migrated in machine direction and cross direction of the cotton nonwoven web. Calibrate the measurement software, then use it to measure the true length of the fiber, and change the needle punching number of time, needle punching depth to fiber the influence of the actual length, arrange the influence of the angle to the fiber with the change study of this fiber length. The result shows that the black polyester fiber in one punching zone of CD direction, the deep of needle in 12mm and 14mm that the fiber lengths distribute at 5.0 to 4.4cm. Then the deep of needle in 16mm distributes at 4.2 to 3.9cm. In two punching zone of CD direction, the fiber lengths distribute at the 4.0 to 3.6cm. In one punching zone of the MD direction, the deep of needle in 12mm that the fiber lengths distribute at 4.6 to 4.1cm. Then the deep of needle in 14mm and 16mm distribute at 4.2cm to 3.7cm. The two punching zone of MD direction, the deep of needle in 12mm distribute at 4.2 to 3.8cm. Then the deep of needle in 14mm and 16mm distribute at 3.6 to 3.0cm.
