Abstract: To improve the non-cooperative weak targets detecting and tracking of monopulse radar in space aircraft launch site, a particle filter track-before-detect method with CFAR based particle weighting is proposed in this paper. The Monte Carlo simulation experiment shows that the method can provide 95% tracking with distance error less than 6 m and velocity error less than 15 m/ s,as to a emitted signal of 0. 8 μs width. And the experiment of real data shows that the method can track non-cooperative weak target stably, and the detection range can be doubled at least.