The radar target characteristic effect caused by different gaps in different surfaces is studied. Firstly, radar cross section characteristic of different benchmark targets are analyzed. Secondly, scattering characteristic calculation and series test on target with different typs of gaps are investigated, from which the single scattering characteristic of gap can be obtained. Finally, the effect of gaps on radar target scattering characteristic is derived. Calculation and experimental results show that compared with gap, groove has a higher scattering amplitude while serrate gap has lower one. The almond body target can simulate the scattering of gap in curve surface more effectively. The conclusion affords foundation for the aircraft radar stealth design.