This review begins by elucidating the rationale for selecting phase optical time domain reflectometry (Φ-OTDR) based on coherent detection as the subject of study, underscoring the necessity and significance of analyzing noise suppression methodologies. With the aid of I/Q demodulation process for phase extraction, the review analyzes the impact of noise on phase-extracted results in coherent Φ-OTDR. Subsequently, nine specific implementable pathways to mitigate noise effects are explored within three categories: amplitude signal, phase signal, and the data itself. For each pathway, the review summarizes the advancements in noise suppression research, providing a typical implementation case to deepen the reader’s understanding of noise processing principles and techniques. Finally, the review not only identifies the shortcomings but also provides insights into noise processing in coherent Φ-OTDR, underlining the current limitations and suggesting potential avenues for future investigation.