The work aims to prepare nanocellulose based magnetic composite film of tea stalk with flexible, transparent and good mechanical properties in a convenient and economic way. First, cellulose nanocrystals (CNCs) from tea stalk were used as templates to synthesize magnetic CNCs (MCNCs). Then, the MCNCs were dispersed in the solution of nanocellulose fibrils (NCFs) from tea stalk. Finally, magnetic composite film was prepared by vacuum filtration method. The magnetic CNCs, which had good superparamagnetism, could be evenly dispersed in the solution with no dispersing agent. The magnetic composite film had good transmittance, mechanical property and magnetic property. The transmittance, tensile strength and magnetization intensity were respectively 71.3%, 75.03 MPa and 12.96 A?m2/kg when the mass fraction of NCFs was 60%. The magnetic CNCs have good dispersion and magnetic property. The magnetic composite film has better magnetic and mechanical properties and it may be considered to be applied in the fields of electromagnetic shielding and magnetoelectric switches.