This is a description of team xuzijian629’s treedepth solver submitted to PACE 2020. As we use a top-down approach, we enumerate all possible minimal separators at each step. The enumeration is sped up by several novel pruning techniques and is based on our conjecture that we can always have an optimal decomposition without using separators with size larger than treewidth. Although we cannot theoretically guarantee that our algorithm based on the unproved conjecture can always give an optimal solution, it can give optimal solutions for all instances in our experiments. The algorithm solved 68 private instances and placed 5th in the competition.