This paper measures and studies the penetration effect based on the capture time of ballistic missiles by early warning radar. Aiming at the problem of low-altitude penetration of ballistic missiles in the face of early warning radar detection, by analyzing the characteristic parameters affecting penetration, the influencing factors of the capture time of ballistic missile penetration and the whole process of low-altitude penetration are clarified. The attack-defense confrontation calculation model of ballistic missile velocity, threat angle and its own radar cross-sectional area ( RCS ) value. The influence of capture time on ballistic missile penetration is simulated and analyzed. The results show that in the face of early warning radar, the capture time of different ballistic missiles increases with the increase of radar cross section ( RCS ) of incoming missiles, and decreases with the increase of velocity.