Because the reflection cross section of stealth target is too small, the detection effectiveness by active detection method is limited. Active and passive joint detection is an effective way. The characteristics of passive detection is analyzed. Based on “am”(atmospheric model), a modeling and simulation method for stealth target with THz passive sensing is established according to the requirements of detecting hiding aircraft from ground-based and space-based. The analysis of comprehensive indexes is conducted combined with remote sensing system. The basic technical requirements of this task are concluded.