The invention is concerned with an oven washing method with high cleanness of leaning heat preservation oven for founding Al alloy flat ingot belonging to colored metal founding field. It relates to heat preservation oven, mouth of oven, turning sliding groove, ACD gas removing sliding groove, let sliding groove of CFF filtration box, expert sliding groove for washing oven, box of residue to founding well, bracket, base of dummy head and muscle plate. The medium is made of turning sliding groove, ACD gas removing sliding groove, let sliding groove of CFF filtration box, expert sliding groove for washing oven and box of residue. Inject residual aluminum liquid of hearth to the box of residue to founding well, and complete the washing process of oven. It improves the unreasonable making process to transfer the residual aluminum liquid at the turning sliding groove by adding the washing process of oven to increase the efficiency and reduce the work intension and product cost. It fits forthe found field of aluminum and aluminum alloy.