A code rate control method and apparatus, an image acquisition device, and a readable storage medium are provided. The method includes: acquiring the gain and exposure time of an image to be encoded from an image processing module of an image acquisition device; obtaining corresponding reference distortion degree according to the gain and exposure time of said image; calculating the difference between the distortion degree in a characteristic region of said image and the reference distortion degree; calculating a distortion tolerance degree of macro blocks constituting said image according to the difference between the distortion degree in the characteristic region of said image and the reference distortion degree; performing macro block predictions on the respective macro blocks in said image, to obtain an optimum macro block prediction mode; and encoding said image, which corresponds to the optimum macro block prediction mode.