A one-dimensional thermal dynamic model and three dimensional CFD model about the intake pipe for a specific aero-piston engine were established respectively for analyzing intake uniformity. These models verified the phenomenon about intake uniformity when the engine worked under external characteristic condition and figured out the causality of this phenomenon. An intake system was designed. The intake uniformity phenomenon could be improved by taking this intake system. The calculation results showed that: by adopting the new intake system, the engine's intake air non-uniformity decreased from 20% to 6% when the engine was at 5 000 r/min. By using this intake system, the average air intake quality increased by 19% when the engine was at 5 500 r/min, the maximum air intake quality increased by 34.1% and the minimum by 12.9%.