Aiming at the high-temperature rotating blade with composite cooling structure of a gas turbine, the high temperature flow field on outer gas side and the inner cooling flow fields in the double cambers with serpentine baffling passages and composite cooling structures were simulated using the gas-thermal coupling numerical simulation method. The influence of the presence or absence of ventilating hole on the cold air flow resistance characteristic and the heat transfer performance were investigated. It is found that the air film/impingement/turbulence composite cooling structures used in the serpentine passages inside the blade without ventilating hole design have a better heat transfer performance, and both the internal and external surface temperature distribution are in a reasonable range under the given cold air flow flux. However, the total pressure supplied by the inlet of the cooling air is too large, which is resulted from the higher flow resistance of the entire inner cooling channel. By the design of local ventilating hole, the internal flow resistance is effectively reduced. Under the condition that the heat exchange effect is only slightly influenced, the required cold air supply pressure and the cold air volume are both significantly reduced, and the air volumes for the double cambers get a better match. The prototype blade has a better engineering application by the redesign.