Portable air flow meters are widely used for measuring air flow rates in the field. To cover broad range of flow rates, multi nozzles are generally used. If ASHRAE standard for installing nozzles is applied, the device gets large and heavy, and becomes difficult for compact sizing and handling. In order to overcome this problem, computational fluid dynamic(CFD) simulations were performed to identify the factors that can make the size of the air flow meter smaller. With help of numerical simulation of which the accuracy was verified by the experiment, the necessary area for multi nozzle installation can be reduced by 47%. Based on the modeling of CFD, a portable air flow meter was manufactured and compared with an air flow measurement device that is compliant with ANSI/ASHRAE 51-1999. Nozzles and dampers which affect the length and cross-sectional size of an air flow meter were selected and improved to suit the portable type. A portable small scale multi nozzle flow meter with exit pressure control that was developed in this study has advantages of small size and acceptable accuracy in the field measurement which showed an error of 0.93%.