In order to study the effect of the flow rate of the cooling air hole on the leakage flow of the turbine blade tip,a numerical simulation method was used to compare and analyze the threedimensional flow field and total pressure loss under the cooling air flow ratio between 0.05% and 3%. The results show that the tip cooling air can effectively reduce the leakage quality and the total pressure loss caused by the tip leakage flow,the leakage quality is reduced by 80%,and the peak value of total pressure loss is reduced by 38.2%; with the increase of the flow ratio,the inhibition effect of the blade tip cooling air on the leakage flow of the blade tip mainstream is continuously enhanced,and the amount of leakage caused by the mainstream continues to decrease. At the same time,tip cooling air also brings new total pressure loss and the overall total pressure loss increases with the increase of flow ratio continually. There are three inhibition modes of tip cooling air on tip leakage,such as by reducing the energy of the mainstream leakage flow to weaken the leakage flow under cooling air flow ratio between 0.05% and 0.1%,by forming a complete air film barrier in the tip area to inhibit the mainstream leakage flow under cooling air flow ratio between 1.25% and 3% and the above two exist at the same time under cooling air flow ratio between 0.1% and 1.25%. When the cooling air flow ratio is 1.25%,the cooling air forms a complete air film barrier in the blade tip area,which prevents the mainstream fluid from forming leakage flow.