As the key component of single junction GaAs/Ge solar cells and GaAs/Ge solar cells, the quality of germanium single crystal affects the properties of space solar cell directly. The dislocation of germanium single crystals is the main impact factor on solar cells efficiency. Through measuring dislocation densities in the different positions of 4 inch <100> germanium single crystals produced by Czochralski method, we found that flower-shaped structure dislocations pattern was mainly caused by the inclusions. This paper briefly analyzed dislocations produced by inclusions, chemical etching pits method. SEM and EDS measurement methods were also employed to study the flower-shaped structure defects. A germanium single crystal with low dislocation density was obtained and the special defects were almost eliminated. The germanium single crystal with low dislocation density (PV) was obtained, which could meet the requirement of the GaAs/Ge solar cells.