Abstract: For the problem of normal integrator exists serious collapsing loss when detecting spare scatterer targets, and Scatterer Density Depend-Binary Integrator (SDD-BI) exists signal to clutter ratio loss when detecting dense scatterer targets, a Double Threshold-Constant False Alarm Ratio (DT-CFAR) detector of range-spread target is proposed by using the density and amplitude of a target scatterer. The formula relating false alarm probability and detection probability to detection threshold is deduced in the Gaussian clutter background, and the optimal first threshold for different target parameters is given. Experiment results show that DT-CFAR has better detection performance for diverse scatterer density targets and has robustness when the scatter density of a target is estimated mismatching.