Stealthy approach method of fighter was researched for the requirement of concealment counterwork in air combat. Detection threat model for radar was constructed based on dynamic trait for Radar Cross Section (RCS). Guidance model was constructed based on parameters for situation description in air combat. An optimal control was formulated for stealthy approach problem of fighter, in which performance index is built by minimizing detection probability and threat restriction is given by critical exposed distance under given detection probability. Receding Horizon Control (RHC) was introduced for online optimization and Gauss Pseudo-spectral Method (GPM) was adopted for numerical solution to assure the real-time resolution requirement. Simulation result shows that stealthy approach ability is greatly enhanced for fighter by adopting both path restriction and performance index restriction, and the model resolution time can satisfy the real-time requirement for fighter control.