A variable length encoding (VLE) device of an image compression system is suitable for encoding transformed and quantized block image signals. The VLE device includes a plurality of encoding modules, for performing VLE on the block image signals; and a selection module (VLE module start controller), for selecting a number of the encoding modules in turn to encode the block image signals. The encoding modules are configured for parallel processing, and an operating frequency of each of the encoding modules is a fractional frequency of a throughput rate of the image compression system. The VLE device is not affected by the time consumed by the VLE in the image compression process, and enables the entire image compression system to operate as desired and achieve the required throughput rate.