The invention discloses a separating and screening method of a source sludge reduction strain. The separating and screening method of the source sludge reduction strain comprises separation of strainsand further screening of the strains, and comprises the following steps: taking fresh sludge of a sewage treatment plant, loading the fresh sludge of the sewage treatment plant into a glass container, conducting sealing, and conducting shaking culture to obtain acclimated activated sludge; coating a sludge-containing sterile agar plate culture medium with supernate, subjected to gradient dilution, of the activated sludge, and after inverted culture is conducted, selecting strains, with transparent circles, around colonies for plate streaking purification to obtain purified bacteria; and taking the separated purified bacteria, activating the separated purified bacteria on LB culture media respectively, taking the strains at the same growth stage, adding the strains at the same growth stageinto glass containers containing sludge with a certain concentration with adding amounts controlled to be the same, carrying out a shake test at a normal temperature, conducting sampling at a fixed interval, comparing obtained samples and a sample without strains, recording data, and conducting plotting according to the data to obtain a dominant strain. According to the dominant strain screened out by means of the separating and screening method of the source sludge reduction strain, without any optimization treatment, the largest sludge removal rate is higher than that of the blank sample by12.2%.