The negative refractive index characteristics of one-dimensional photonic crystal consisted by Fibonacci multi-layer films has been studied by numerical method.The refractive indices for two materials,which are used to construct the Fibonacci multilayer films,are 0.920 and 0.999,respectively.The calculation result shows that,on one hand,there are several negative refractive index zones for this kind of photonic crystal even if the refractive indices are very small; on the other hand,the difference is very large for the frequency between the zones.As an example,a kind of transmission-type plano-concave lens is designed.The simulation of the electromagnetic field distribution for the lens demonstrates that the lens can focus the incoming X-ray radiation.At the same time,the calculation of the absorption strength and refractive indices for real materials shows that not only there are large differences for the absorption strength with different materials,but also the refractive indices for real materials are different in X-ray band.Obviously,the characteristics above support a kind of transmission-type lens using in X-ray.