Abstract: Based on a model and energy analysis of heat and mass transfer of air and water in a direct contact forward flow, a set of general equations which express the internal relationship among the state parameters of air and water and dimensionless parameters of transfer process such as number of heat transfer NTU_h, number of mass transfer NTU_m and ratio of water with air flux were deduced theoretically in this paper for the purpose of obtaining calculation equations and method about heat and mass transfer of air and water in a direct contact forward flow, and for producing a theory and a new method on designing evaporation cooling equipment and analyzing experiment data. A method by use of MATLAB to solve general equations was also proposed. Using the general equations to the isoenthalpy process, the theoretical conclusion is the same as previous theoretical result. Calculations and analysis for a cooling-dehumidifying process show that an inherent relationship among NTU_m, NTU_h and β exists and there is minimum of β while the inlet state parameters of air and water are given, and while β is consistent and NTU_m is increased to a certain value, NTU_m has no influence on the results, while NTU_m is consistent, there is a β corresponding to a maximum temperature falling for air.