The disclosure provides a load balancing method, a load balancing system, a load balancing device and a topology reduction method. The load balancing method includes configuring a transmission progress value for each of the edge servers; grouping the edge servers into server groups, wherein each of the edge servers is grouped into at least one server group among the server groups; receiving a download request corresponding to a first video stream from a user device, wherein a first server group among the server groups provides the first video stream; and selecting one of the edge servers from the edge servers of the first server group as a first edge server to provide video data of the first video stream to the user device according to the transmission progress values of the edge servers of the first server group.