In order to get a micro axial turbine pneumatic performance and optimal design project, full threedimensional (3D) computation of the turbine flow field is conducted by the computational fluid dynamics (CFD) software CFX14.0.3D Reynolds averaged N-S (Navier-Stokes) equations with shear stress transport (SST) turbulence model were used to predict the micro axial turbine internal flow, which results were compared with the experimental data and they were well matched. The internal flow condition in each working point was obtained by computation and for the turbine performance curve. The gas turbine engine had smooth performance curves and narrow working range. The efficiency of designing point was 0.805, which is lower more than that of large engine turbine. The computational results provide certain reference and basis for the design of an advanced micro axial turbine of aviation engine.