To describe accurately the dynamic physical process and obtain quantitatively boron (B) spatial distribution as well as it's evolution behaviors in silicon (Si) under boron implantation, we built a multiscale dynamic model of charged defects. In the model, multiple microscopic processes of defects generation and evolution are comprehensively considered under B ion implantation, including charge states of defects and reactions among charged defects, evolution of B-interstitial clusters (BICs) and interactions between charged defects and carriers. The simulated B distribution is consistent with experiments. It shows that BICs dominate the depth distribution of B concentration and interstitial B (B_I) makes B distribution extend into depth. Besides, considering charge states of defects, we correct diffusion coefficients of Si interstitials (I) and B_I so that the behavior of B distribution can be described accurately. The model reveals real physical processes and micro-mechanisms in Si under B implantation, which demonstrates that BICs and real charge states of defects are the key in describing B distribution. It provides theoretical guidance for semiconductor device fabrication.