In order to meet the urgent requirement of large flow simulation in low speed wind tunnel for engine inlet test, a design scheme of columniform distributed ejector for 4 m-scale low speed wind tunnel was proposed. The internal flow filed of ejector was simulated by ANSYS-CFX software using the finite volume method. The design parameters were optimized, including the ejecting area rate, discrete distribution of nozzles and the design point total pressure and Mach numbers of nozzle outlet. The improved design of ejector met the limited condition in wind tunnel and the acquirement of large mass flow, and solved the contradiction of small size and large mass flow. The experiment in FL-14 wind tunnel indicated that the max absorbing mass flow rate of improved ejector can reach 9.07 kg/s, fulfilling the large mass flow needs of inlet test in 4 m-scale low speed wind tunnel.