The present invention relates to a WDM/SCM-PON and a media access control method for asymmetric packet communication in the same. In the WDM/SCM-PON, each SCM channel is classified and used as a link by adopting an SCM technique of subdividing a wavelength band of up/downstream data links between an OLT and ONTs into frequency bands, and the ONTs are formed so that a certain SCM channel is independently distributed not fixedly assigned. Accordingly, an inventory problem, which can be generated in WDM/SCM, is prevented before happens, asymmetric dynamic band allocation is performed, and asymmetric service of up/downstream transmission is supported. As a result, a band required for next generation service is dynamically provided, optical interference effect is minimized, and Ethernet compatibility is provided so that Ethernet service suitable for providing IP service can be accommodated.