Abstract: A mathematical model for designing even hole air discharge of perforated PVC film duct was set up. In the model, structure characteristic of duct, static pressure, flow rate and air performance of entrance and air pressure of animal house were considered comprehensively. An equation for modifying temperature inside duct was first used in this model and the calculated error was decreased greatly. Through the characteristic experiment to five PVC film ducts with different hole spacing, a series of design parameter was recommended under the allowable error(±10%)of hole discharged air volume per unit length.