The invention provides a sputum exfoliated cell preservation liquid with capacity of effectively improving a sputum specimen retention method and a slide preparation method as well as a preparation method of the sputum exfoliated cell preservation liquid. The sputum exfoliated cell preservation liquid is mainly prepared from polyethylene glycol-400 as a cell protecting agent, dithiothreitol as a mucus decomposer, ethyl alcohol as a cell stabilizer and the like. With the application of the sputum exfoliated cell preservation liquid, sputum can be preserved once spit, so that the sputum retention method is regulated, sputum collection time and storage time are prolonged, and cells in the sputum are prevented from autolysis and denaturation; meanwhile, the sputum treated with the preservation liquid can be applied to preparation of slides from liquid based thin-layer cells, therefore, the collection quantity of the cells is increased, the slide preparation effect is improved, and positive rate of sputum exfoliated cell detection is effectively increased. After application of the technology, sputum exfoliative cytologic examination can be simpler, more convenient, easier, safer and more economical and can be more easily popularized and used, and the sputum exfoliated cell preservation liquid and the preparation method thereof can be one of main methods for early diagnosis and screening of lung cancer, thereby effectively increasing early diagnosis rate and recovery rate of lung cancer and bringing benefits to humans.