The results of an experimental study of exhaust duct aerodynamics of a two-shaft gas turbine of medium power made at the Turbomachinery Laboratory named after I.I. Kirillov of the Peter the Great St. Petersburg polytechnic university are presented in the study. The experiments were performed on a model consisting of an exhaust diffuser and a collector box, by traversing the flow at the cross-sections of the flow channel of a model output duct. The goal of the study was to determine the integral characteristics of the output duct: the kinetic energy losses of the flow and the pressure recovery coefficient at various sections of the path, as well as obtaining experimental data for validating the CFD flow model. As a result of the experiment, the main sources of kinetic energy losses in the flow channel were identified, the generation mechanism of vortex structures after the struts and in the outlet collector box was discovered and ways to improve duct aerodynamics were determined. A more detailed analysis of the flow in the duct can be obtained only by numerical simulation. Therefore, an important result of the work is the experimentally measured 3D fields of the flow parameters at the flow duct cross-sections, which are necessary for testing the CFD flow model and performing a numerical experiment.