The invention relates to a cellulose composite solvent system and application thereof. The composite solvent is composed of the following constituents in percentage by weight: 6%-12% of NaOH, 4%-15% of urea, 4%-15% of thiourea, 0.5%-3% of ZnO, 1%-3% of polyacrylamide and 52%-84% of H2O; and the composite solvent is used for preparing a cellulose spinning solution, and the preparation comprises the following steps of: baking the cellulose powder, pre-freezing, preparing cellulose solution, and processing in a twin-screw extruder, thus obtaining the cellulose spinning solution. The composite solvent system is convenient for preparing the cellulose spinning solution, can effectively dissolve the cellulose under the condition of low temperature and high shear, and is non-toxic and non-volatile, simple and easy to recycle, and low in environment pollution, so that the cellulose can be used widely as a renewable energy substance.