The invention relates to compression ratio adjustment method and electronic device of a JPEG (Joint Photographic Experts Group) video, used for adjusting the file size of a JPEG graphic file. The adjusting method comprises the following steps of: obtaining an original video; loading a compression parameter lookup table, and obtaining a first compression parameter and a second compression parameter according to the compression parameter lookup table; compressing the original video by respectively using the first compression parameter and the second compression parameter to obtain a first file size and a second file size of the compressed original video; setting the size of a target file; computing a target compression parameter according to the sizes of the target file, the first file and the second file; and loading the target compression parameter to compress the original video for outputting a target video.