The Geiger-mode APD is very sensitive. For this advantages, it is widely used for astro-observation, particle physics, LIDAR. Sky background noise is a big problem for Geiger-mode APD detector during the day. The detection statistical model in theory was built, False alarm probability and detection probability and finding the way to increase maximum detection distance in difference detection threshold and background noise were discussed. In difference background noise, the maximum detection distance was determined. By limiting the filter bandwidth or reducing the detector open time, the background noise photon number is reduced to 2. The success rate of detection at 900Km is 96.6%. To the non-cooperative target, when the radar scattering cross section is 1 m2, the success rate of detection is 70%.