Bit rate control method and device for image compression

The invention provides a bit rate control method and device for image compression. The bit rate control method comprises the following steps of: obtaining image complexity of a color passage in a space domain image data according to the space domain image data of an image; estimating a corresponding zoom coefficient for the color passage according to the image complexity and a target bit rate; and when performing the image compression on the image, quantizing the frequency domain image data of the image according to the estimated zoom coefficient corresponding to the color passage.