In situ detection of extraterrestrial life is significant for scientific research and humanities. In future exploration missions， marine worlds such as Europa are gradually becoming new subjects of interest. Considering the application of digital holography in deep-sea microbial in-situ detection， the application of digital holography in the in-situ detection of extraterrestrial life is proposed in this study. The research progress of digital holography for extraterrestrial life detection is investigated， and the two technical solutions of common mode and lensless digital holographic microscopy proposed by the Gene Serabyn team are summarized. Digital holography for extraterrestrial life detection is in the laboratory-research and development stage； in situ detection of marine microorganisms at low temperature and low cell concentration is the basis for the detection of extraterrestrial life， and the feasibility of the proposed idea has been indirectly verified. Digital holography is an ideal solution for realizing the detection of extraterrestrial life. The optimization of digital holography for in-situ detection of microorganisms in the earth's oceans can lay the foundation for future extraterrestrial life detection missions.