Abstarct: Airlift pumps are finding increasing used where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids in nuclear applications must be handled and when a compressed air is readily available as a source of a renewable energy for water pumping applications. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters. For this purpose, calculated effects of the main parameters on the performance of an airlift pump, after designing and testing of an air-lift pump, as like as air inlet pipe diameter, submergence ratio of the riser pipe, number of air inlets and air mass flow rate. The present results showed that The maximum efficiency does not occur at the maximum water mass flow rate,The air-lift pump lifted maximum amount of liquid if operated in the slug or slug-churn regimes and As the submerged ratio increases, the maximum efficiency of the pump increases at the same air-flow rate. In this study, numerical simulation is used for quality comparsion between flow regime maps avservating in experimental work and numerical model. openFOAM CFD package codes used for numerical model. This package is baxsed on Volume of Fluid (VOF) method that is used for simulation bubble rising in stagnant liquid. Slug flow is Choiced for numerical modeling because is the great part of flow regim maps at the optimum performance of the airlift pump. flow regime maps avservating in experimental work gives a good agreement with flow regime maps of numerical model.