Results of experimental and numerical research of the block «last turbine stage — exhaust diffuser» are shown on an example model turbine V84.3. The comparing of block integral characteristics were performed for the model with symmetric struts, and correlation analysis of diffuser impact on improving quality of the unit was made. Statistical analysis of the deviations between the calculated and experimental flow velocities at the control plans on the basis of experimental measurements of 3D-velocity flow fields had been carried out.