Lignin is abundant in nature and it is good materials for carbon fiber, but the mechanical strength of the carbon fiber prepared by the lignin extracted from the paper mill waste is low. In this study, nanocellulose whisker (NCW) was used to reinforce lignin and the NCW/lignin composite fibrous film was prepared by electrospinning. By scanning electron microscopy (SEM), single fiber strength tester, the morphologies and mechanical properties of the composite films were researched; the influence of the mass fraction of NCWs on the mechanical property of lignin fibrous film was studied. In the range of this experiment, the results show that adding NCWs into lignin improved the spinnability of lignin, with the increase of the content of NCWs, the mechanical property of lignin fibrous film increased, but there is an optimum content of NCW and the NCWs must be dispersed evenly in the lignin. As the content of NCW increased from 0.3% to 5.0%, the tensile strength and modulus of NCW/lignin fibrous film increased, but the elongation at break decreased. The spinnability of lignin will be worsen if the contend of NCW was more than 5.0%.