The incoherent flexible fibre, made through matched drawing by using SiO2-B2O3-La2O3-Nb2O5-RO systematic glass as core and using low refractive index material made by ourselves as cladding, has a numerical aperture of 0.8725 and on angle of light reception of 122°. It enlarges the observing scope of the medical fabric endoscope on the pathological changes of inner cavities of human viscera. It satifies the special requirement of observation and diagnosis on medical apparatus and instruments.In this article, the scope of the fundamental composition of SiO2-B2O3-La2O3-Nb2O5-RO system is desgivened, the requirement on the properties of the materical which is used to make large numerical aperture fibre is discussed, some factors which have influence on the performance of fibre are analysed, and the result of preliminary research is given at the end.