Collagen fiber film is one of the important edible protein films, but its performance is affected by a variety of external factors. In order to improve the performance of collagen film and make it more suitable for food packaging, this study investigated the effects of different pH values (2, 3, 5, 7, 11) and different ionic strengths (0.1, 0.2, 0.3 mol/L) on the mechanical strength and microstructure of collagen fiber film. The experimental results showed that the pH had no significant impact on film thickness, whilst the tensile strength and elongation at break of the films exhibited a V-shaped change with increasing pH, with the highest tensile strength of 67.67 ± 2.57 MPa occurring at pH 2 (where smooth and uniform film surface was observed). With the increase of ionic strength, film thickness and roughness increased whilst the mechanical strength decreased significantly, along with a disrupted fiber arrangement. Compared with the dry film, the tensile strength of the wet film reduced greatly whilst the elongation at break increased considerably. In addition, the swellability of the film increased, as the ionic strength rose and the pH of the film-forming solution deviated from the isoelectric point of the collagen fiber.