Shale oil is a kind of unconventional oil and gas, which is rich in reserves and has become an important strategic replacement resource for conventional oil and gas resources. However, the formation of shale oil resources is unique, and the characteristics of shale oil resources are different from those of conventional oil and gas resources. Shale oil is an unconventional oil resource occurring in reservoir rock series dominated by organic shale. Shale is not only the source rock of shale oil generation but also the reservoir that accumulates and preserves shale oil. Shale reservoirs formation is affected by many factors. This paper summarizes the research achievements on the main influencing factors of shale reservoirs formation at home and abroad in recent years, including (1) organic carbon content; (2) organic matter maturity; (3) organic matter type; (4) reservoir burial depth; (5) porosity; and (6) microscopic pore throat structure. This paper not only summarizes the previous research but also puts forward some suggestions for the future research direction. This paper has a certain reference value for a comprehensive understanding of shale reservoir formation.