Organic solar cells involve processes such as the generation, separation, and transmission of photogenerated charges, which directly affect their efficiency and stability. Femtosecond transient absorption spectroscopy (fs-TAS) is an effective technique for understanding the dynamics of photogenerated electron transfer. By measuring the response to femtosecond laser pulses, fs-TAS provides deep insights into the photoexcitation and energy transfer mechanisms in optoelectronic materials, helping optimize material performance. This review summarizes research on femtosecond time-resolved absorption spectroscopy in organic solar cells and contributes to the understanding of this research field both domestically and internationally. It comprehensively introduces the working principles, hardware equipment, and data processing of fs-TAS and two-dimensional electronic spectroscopy, followed by discussing their application progress in the photogenerated charge dynamics process of organic solar cells. Finally, future developments in organic solar cells are discussed. This review aims to serve as a reference for peer researchers in femtosecond time-resolved absorption spectroscopy.