Aiming at the current deep roadway support shotcrete there are mechanical properties of low, toughness deficiency poor and other problems, the effects of polyoxymethylene (POM) fiber admixture (0, 5, 7, 9 kg/m3) on the mechanical properties of roadway support shotcrete were analyzed by four-point bending test and SEM technology. The results show that POM fiber can significantly improve the mechanical properties of concrete, of which the flexural strength is most significantly increased (89.46%), compressive and splitting tensile strength are increased by 43.48% and 62.71%, respectively, and the toughness effect is the best when the dosage is 7 kg/m3. In the macro and fine mechanical properties, the residual flexural strength retention rate is more than 30%, which effectively inhibits the development of cracks and reduces porosity, while significantly attenuating the brittle damage characteristics of the material; in the micro scale, the fibers inhibit brittle damage through interfacial frictional energy dissipation and three-dimensional load transfer, and their surface stripe structure enhances the mechanical occlusion as well as the fibers have two forms of pullout and pull-off. The research results can provide theoretical and technical support for POM fiber in the field of tunnel support.