Abstract: An experimental study on the influence of the variation of balance hole area on the aerodynamic performance of turbine was carried out with a three-stage air turbine test bench. Numerical calculation and analysis of the test turbine stage were carried out, and the rule of the turbine stage performance change with the balance hole area was studied, and the numerical results were compared with the test results.Results show that the stage efficiency is the lowest when there is no balance hole, and for the balance hole with diameter less than 25 mm, the stage efficiency increases with the increase of balance hole diameter, and then decreases gradually. The calculated efficiency change rule is in good agreement with the experimental results. The efficiency is optimal when the leakage area ratio between the balance hole and the diaphragm seal is 2-3.