The biggest clinical benefit of OCT as a diagnostic tool for retinal disorders is that it enables the discrimination of subtle pathologic changes in vivo. Though a large number of researches have been done to expand its applications, few of them proved sufficient utility in clinical settings. In laryngology, an OCT system attachable to and working in tandem with an operating microscope may provide solid clinical benefits. Nevertheless, such a system has not been introduced yet, while it is more common to find an OCT system with a hand-held type probe. Hence, we developed a phonomicrosurgical OCT with a long working distance and attachable to an existing operating microscope. The OCT also has a dichroic mirror which splits the coherent IR laser and visual projection to enable dual imaging. We evaluated the efficacy of the system in evaluating subepithelial tissue structure, especially in the Reinke’s space of vocal fold. We tested its imaging capability with excised canine larynx and eyeball. Then, we assessed the surgical margin with the OCT images after treating a live canine larynx with a CO2 laser under general anesthesia. In addition, we compared the images with corresponding histopathologic findings to confirm the diagnostic feasibility. The OCT and histopathologic images showed a significant correlation to identify the epithelial layer, lamina propria, subepithelial glandular structures and vessels from the OCT images. This is the first OCT system attachable to an operating microscope which may provide a promising alternative to frozen biopsies for intraoperative laryngeal cancer margin assessment.