In this paper, all main physical dimensions representing the properties of the complex interior circulation air cleaning system have been derived. Proceed from balance of materials, these physical dimensions have been sorted out to be dimensionless similarity criteria, from which a conception of cleaning criterion is advanced and appropriate criterion equation have been derived. This equation subtly reveals the inner relationship among various important physical dimensions of possible system design projects correctly, simply and clearly. With various economical parameters, it can be found very easy and believable to carry out work from technique & economy comparison among various design projects to optimum design.