Sewage impurity separation method capable of realizing cyclic on-line cleaning

The invention relates to a sewage impurity separation method capable of realizing cyclic on-line cleaning. The method comprises the following concrete steps that: sewage enters an impurity screening zone from a water inlet pipe, sewage enters a concentration impurity zone at first, and after an effective liquid level is reached in the concentration impurity zone, effluent penetrating a mobile micro-screen enters into a water outlet area which seems to be wrapped by two layers of mobile micro-screen, is then collected by a water outlet pipe and is discharged from a system or enters a next-stage screening system; an aeration pipe located at the bottom of the impurity screening zone uninterruptedly washes the mobile micro-screen, and the mobile micro-screen is driven by a drive unit to cyclically pass through the impurity screening zone, a slag clearing zone, a washing zone and a soup soaking zone, wherein the filtering performance of the mobile micro-screen is recovered on line; and concentrated impurities are