Schizoid personality disorder (ScPD) is a rare mental disorder, the field is young, and related research is not welldeveloped. This review used a systematic search on Google Scholar about researches on ScPD and fundamental information. The main purpose of this paper is to grow knowledge of ScPD and improve understanding of this personality disorder by providing an overview of its characteristics, symptoms, etiology, impacts, and treatments. Psychologists proposed several treatments that may alleviate ScPD symptoms. Related treatments include socialization group which may partially help with their social activity, medications specific for schizophrenia and only use on ScPD as they share similar negative symptoms, and psychodynamic psychotherapy, which lack qualitative and quantitative research in this area. Although treatments suggested are supported by researchers, the field has not developed a targeted one. The difficulty in treatments and developing treatments may be due to patients' special symptom, which is lack of motivation. Anyhow, future research should target effective treatments especially, and provide more case studies. More experiments about etiology are also important, which may help identify the complex etiology of ScPD or develop targeted medications. The future directions of developing the field of ScPD are suggested.