To quickly and efficiently calculate the cooling characteristics of double wall composite cooling structure used in turbine blades, a set of pipeline network coupling algorithm which is enforceable for air-cooled blade simulation has been applied to the designed double wall cooling blade. Combining with one-dimensional pipeline network method and interpolation process between blade wall unit and corresponding outflow field grid, HIT3D-Coolnet pipeline network coupling procedure is composed, and the simulation validity of this algorithm has been verified by turbine blade test data. For the new-style cooling technology of double wall cooling structure, three compound cooling schemes have been preliminarily constructed. The HIT3D-Coolnet quickly gets blade outer wall temperature information to select the initial scheme. With the flow characteristics analysis of double wall structure of the primary scheme by full three-dimensional numerical simulation, measures have been taken to improve the initial design. Flow field analysis shows that the cooling air introduced into the narrow cavity impacts the chamber wall, forms specific vortex structures which can effectively enhance the internal convective heat transfer. Under the reasonable cooling distribution, the double wall cooling technology can obtain relatively good cooling effect.