Abstract: The cross-section shape of the cross-hollow fiber was screened and tested by using computer in combination with the polarized light microscope image acquisition and analysis system,and the characterization method of the shape factor was studied.The shape factor of the fiber,such as shape factor in radius,shape factor in cross section,branch factor and volume content,was tested and compared.The cross-section shape of cross-hollow fiber was compared with that of the hollow fiber.The novel method of equivalent diameter or average diameter was brought forward to characterize the characteristic shape coefficient of the fiber.The results of the study indicated that the adopted method is rapid,simple,accurate and convenient and has practical value.