Developing the green dielectric materials satisfies the requirement of the sustainable development of society and economics. In this work, glutaraldehyde (GA)-assisted crosslinking strategy was developed to prepare the crosslinked regenerated cellulose (CRC) films, and the effects of different crosslinking methods, including crosslinking steps, concentration of GA solution and crosslinking time, on dielectric and mechanical properties of the CRC films were systematically investigated. Microstructure and morphology characterizations show that compared with the common RC films, the CRC films show apparently reduced defects and enhanced intermolecular interaction. At GA concentration of 6 vol% and crosslinking time of 30 min, the CRC film shows the lowest dielectric loss (0.03 at 1000 Hz, 92.3% smaller than RC film) and the highest breakdown strength (336.55 MV m-1, 364.3% higher than RC film), and simultaneously, the film shows the high tensile strength of 76.8 MPa and excellent tensile modulus of 6.08 GPa, about 240.9% and 104% higher than those of RC film, respectively. This work provides new insight in tailoring the dielectric and mechanical properties of the cellulose films through constructing the crosslinking structure, which is of great significance for the fabrication of the high-performance cellulose-based dielectric materials.