Abstract: The innovative ideas of a high power density micro-turbojet engine with a thrust 100 N and a rotational speed 100 000 r/min were presented in this paper.And,the research focused on the new design feasibility of the main shaft inner cooling channel,especially on the pumping air mass flow capacity of the simple front nut micro-pumps.The flow field and the temperature field of the main shaft inner cooling channel were numerically simulated based on the Navier-Stokes equations.The problem with the boundary conditions coupling was solved by iterative method.The numerical results show that the cooling performance of the main shaft inner channel is determined by the number and structure of the simple front nut micro-pump.The new design of the main shaft inner cooling channel,the simple front nut micro-pump and the numerical method can be applied to the research of other types of micro engines.