A composting technique was assessed to enhance efficiency in oyster mushroom substrate. Poplar sawdusts and by-product of winter mushroom added by 10% of rice bran were composted outdoors at $20^{circ}C$ to $28^{circ}C$ for 12 days. The duration of fermentation was shortened 3 days in fermented sawdust plot. The yield obtained from waste cotton substrate with fermented poplar sawdust was 742 g, whereas the yield from control 663 g. In addition, the substrate with by-product of winter mushroom was the most effective to composting. It was useful to apply the fermented sawdust and by-product to waste cotton for compost and sporophore production of oyster mushroom.