The present invention relates an adaptive video transcoding method and system, the method and the system for considering an available network bandwidth, a characteristic of a video, and a calculated load of a server, and adaptively controlling an encoding option of a transcoder, when carrying out a video transcoding such as a decoding of a video and video editing, and an encoding process, so as to enable a transcoding of a maximum number of videos in a limited environment. The adaptive video transcoding system according to the present invention comprises: a video transcoding device for calculating a minimum required compression rate required by a measured streamable bandwidth, selecting, as a transcoding encoding option, each of encoding options making up an encoding option combination with the lowest CPU usage rate of when at least one encoding option, from an encoding option combination having a greater compression rate of when at least one encoding option is combined and encoded, than the minimum required compression rate, is combined and encoded, and using the selected transcoding encoding option to transcode and transmit the video contents to a user terminal; and a user terminal for receiving and displaying the video contents transcoded according to the transcoding encoding option from the video transcoding device.