Hypertrophic scars (HTS) are predominant diseases after burn and trauma, which cause severe physiological and psychological problems. HTS have been researched for decades, and our knowledge about the mechanisms of HTS formation process has been increasing. However, the effects of currently available prevention and treatment strategies are limited. In this review, we summarize currently known mechanisms and recent studies of HTS, including extracellular matrix, matrix metalloproteinases, fibroblasts, myofibroblasts and their contraction ability, keratinocytes, growth factors, inflammatory and immune response, and stem cell treatment, hoping for a better understanding of HTS generation, development and effective translation to treatment strategies.