The invention discloses a multi-source detection-based method for detecting a stealth target in the sky, which mainly comprises the following steps that: A. an omnibearing radio computing service (RCS) value of the target is calculated; B. possibility for a radar to detect the target is calculated; and C. multi-source detection information is merged. The method is applied in a combat simulation system. Compared to the traditional model, a simulation effect on detecting and discovering a fighter is more approximate to the reality, and higher practicability can be realized.