This invention relates to a regenerated cellulose film, a functional film and preparation method thereof. The method mainly comprises the following steps: (1) shaping a cellulose/ionic liquid solution by die extrusion, calendering and casting; (2) the shaped solution entering into a coagulation bath to form a cellulose gel film; (3) in coagulation and washing processes, stretching the cellulose gel film at least 1 time in the transverse direction and at least 1 time in the longitudinal direction; (4) in drying process, further applying tension to the stretched film in the transverse and longitudinal directions, and finally obtaining a regenerated cellulose film by rolling. An organic and/or an inorganic functional additive can be added into the cellulose/ionic liquid solution to obtain a regenerated cellulose functional film. The regenerated cellulose film and the functional film thereof obtained by the above method have well-balanced and relative high longitudinal and transverse tensile strengths, as well as good flatness.