Honeycomb seal is an important component to reduce the leakage of working fluid of turbine machinery. This paper designs and builds a honeycomb seal leakage experimental device,and uses a combination of experimental and theoretical methods to study the effects of back pressure valve opening λ,rotational speed and inlet pressure on the honeycomb seals leakage. The results show that the experimental results are in desirable agreement with the theoretical calculated values,and the relative error of both is within 6%. At the same back pressure valve opening,the seal leakage increases with the increase of inlet pressure,while with the increase of speed,the seal leakage remains almost constant. Under the condition of invariable inlet pressure and rotational speed,the seal leakage increases with the increase of back pressure valve opening,and the leakage reaches the peak value when the back pressure valve opening is 1. Compared to the back pressure valve opening of 1,when it is 0,the seal leakage can be reduced by up to approximately 15.9%.