Abstract: The importance of stealth penetration ability of military aircrafts is demonstrated via. an analysis of experience of several local wars, the result of a special system engineering research, and the threat of anti-stealth techniques.In this paper, the stealth techniques are classified into four categories: a. techniques against radar detection; b. techniques against infrared detection; c. techniques against acoustic detection; and d. techniques against optic detection.On account of that the major thre~ ats against military aircrafts are, at present, the radar and the infrared detection, the first two have been important subjects of research.Therefore, many effective measures in these categories of stealth techniques are introduced in this paper.In the tactical-technical requirement,the principal aspects representing the stealth penetration ability of an aircraft are: a. the scattering and radiating characteristics of the aircraft; b. the electronic interference ability of the aircraft; and c. the tactical stealth techniques used by the aircraft.The radar cross section levels of some aircrafts which are in service or will go into service are collected.In addition) the inferred values of radar cross section of various types of aircrafts that will appear in the first decade of the 21st century are also listed.