Abstract: A BOD₅-DOparameter inverse coincidence model is set up in this paper according to the verse theory and the dispersed inverse arithmetic method.The Parameter formulas of the coincidence model are educed.The deoxygenation rate,reaeration rate,deposition and suspend once more coefficient,photosynthesis reaeration and abc warfare breath deoxygenation coefficient,andself-clearing coefficient by space arequantitaively calculated also,giving a new approach for water self-clearing rulereserch.