Children's well-being of immigrants is facing several challenges related to physical, mental, and educational risks, which may obstacle human capital accumulation and further development. In rural China, due to the restriction of Hukou registration system, nearly 9 million left-behind children (LBC) are in lack of parental care and supervision in 2020 when their parents internally migrate out for work. Through the systematic scoping review, this study provides a comprehensive literature summary and concludes the overall negative effects of parental migration on LBC's physical, mental (especially for left-behind girls), and educational outcomes (especially for left-behind boys). Noticeably, both parents' and mother's migration may exacerbate LBC's disadvantages. Furthermore, remittance from migrants and more family-level and social support may help mitigate the negative influence. Finally, we put forward theoretical and realistic implications which may shed light on potential research directions. Further studies, especially quantitative studies, are needed to conduct a longitudinal survey, combine the ongoing Hukou reform in China, and simultaneously focus on left-behind children and migrant children.