Abstract: Based on reasonable model hypotheses and the energy analysis of heat and mass transfer of air and water in a direct contact counter flow, a set of general equations that can describe the internal relationship between the state parameters of air and water and dimensionless parameters of transfer process are given. A method utilizing MATLAB to solve these general equations is also proposed.Calculations and analysis with the model of a cooling- dehumidifying process give a consistent result with that of previous experiment.A new method for designing equipment such as evaporating cooler and cooling tower, and for analyzing experiment data of heat and mass transfer of air and water in a direct contact counter flow can be derived from this study.