Route planning in 3-D uncertainty environment, especially when the threats are uncertain, is the trend of the UAV (unmanned aerial vehicle) route planning. Against the opacity of enemy threat information, the threat probability model is adopted to determine the location of the threat, and D-S evidence synthesis algorithm is used to determine the threat strength, then to calls D* route planning algorithm getting UAV flight route and forming the "flying, judging and planning" autonomous planning pattern. Paper also analyzes various threats and then establishes 3-D models for these threats. The method turns out to be feasible by simulation.