The invention relates to a scheduling method of a video trans-coding task based on Map-Reduce, aims to construct an MPEG-4 video decoding time consumption model based on macro block and an H.264/AVC video coding time consumption model based on image frame, so that the trans-coding time consumption of video slices in the video trans-coding task based on Map-Reduce is predicted; the time consumption matrix ETC of the trans-coding expected task of video slices is constructed based on the predicted time consumption; the completion time matrix ETF of the trans-coding node expected task is constructed based on the time consumption matrix of the trans-coding expected task of the video slices; the video trans-coding task is distributed on a video trans-coding cluster based on the completion time matrix of the trans-coding node expected task and the trans-coding time consumption difference threshold Beta.