Turbopropeller powered transport aircraft uses propellers as energy output. Slipstream is an important feature of turboprop which should be considered in airworthiness verification phase. Stall speed is an important parameter to reflect aerodynamics characteristics of aircraft. It is particularly important to consider the influence of slipstream in the verification of stall speed. The influence of propeller slipstream on aircraft aerodynamic characteristics is analyzed. According to the relevant requirements of CCAR25.103, the airworthiness verification idea and specific verification method for the stall speed of turbopropeller powered transport aircraft considering the influence of slipstream are proposed. Taking the wind tunnel test on the influence of slipstream on a turboprop aircraft as an example, the test results of longitudinal aerodynamic characteristics of the aircraft under the condition of engine idle and cruising configuration considering the influence of slipstream are given. The test results further prove the importance of considering the influence of slipstream in stall speed verification, which can provide a basis for stall flight test. The verification method presented in this paper provides references for the verification of stall speed and other airworthiness provisions related to flight performance and flight quality of turbopropeller powered transport aircraft.