One of the major challenges that radar faces comes from the detection of low-altitude escaping weak targets. Modern military is gradually expanding to the low-altitude field, and ultra-low-altitude escape technology is also increasingly developed, resulting in the research on low-altitude escape and weak target detection technology. When the radar performs downward-looking detection on this low-altitude weak target, due to the relatively low flying height of the target, the corresponding scattering coefficient of the target is large, so that the echo of the target is easily submerged in the sidelobe clutter. Different from traditional pulse-Doppler (PD) radar, synthetic broadband pulse-Doppler radar can achieve two-dimensional high resolution of distance and velocity at the same time, and has good coherence and anti-jamming performance. In this paper, a qualitative and quantitative analysis of the characteristics of low-altitude flying targets is carried out, and the clutter environment encountered by the detection is simulated and verified, and a detection method of low-altitude escape small radar cross-section (RCS) targets based on synthetic broadband pulsed Doppler radar is provided, so as to optimize the parameter design to reduce the probability of missed detection.