The response wavelength of the boron doped germanium (Ge:B) blocked-impurity-band (BIB) structured infrared detector can reach 200μm, which is the most important very long wavelength infrared astronomical detector. The ion implantation method greatly simplifies the fabrication process of the device, but it is easy to cause lattice damage, introduce crystalline defects, and lead to the increase of the dark current of detectors. Herein, the boron-doped germanium ion implantation process was studied, and the involved lattice damage mechanism was discussed. Experimental conditions involved using 80 keV energy for boron ion implantation, with doses ranging from 1×10^13 to 1×10^15cm^-2. After implantation, thermal annealing at 450°C was implemented to optimize dopant activation and mitigate the effects of ion implantation. Various sophisticated characterization techniques, including X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS) were used to clarify lattice damage. At lower doses, no notable structural alterations were observed. However, as the dosage increased, specific micro distortions became apparent, which could be attributed to point defects and residual strain. The created lattice damage was recovered by thermal treatment, but an irreversible strain induced by implantation still existed at the high doses.