Abstract: Spent mushroom substrate (SMS) is a byproducts of mushroom cultivation, which uses straw and cottonseed hulls as substrate. SMS is an important middle part connecting plants and animals in the entire ecosystem. Cottonseed hulls were fermented during edible fungi cultivation and was one of raw materials of SMS, which can be used as ruminants feed. Six ruminally cannulated local white wether goats (10 month old with 35.42±3.96 kg initial body weight) were used to evaluate the nutritional value and in situ dry mater (DM), organic matter (OM), crude protein (CP), acid detergent fiber (ADF) and neutral detergent fiber (NDF) degradation characteristics of SMS of Pleurotus ostreatus, Auricularia polytricha, Flammulina velutipes and P. ferulae and cottonseed hulls. The study analyzed the effects of mushroom cultivation on nutritional value and dynamics of rumen degradability of cottonseed hull and four SMS. Compared with cottonseed hull, the results showed that DM and OM of the 4 SMSs dropped by 13.09%~19.67% (P < 0.01) and 14.13%~39.52% (P < 0.01), respectively. CP of the 4 SMSs increased by 40.20%~ 34.29% (P < 0.01), while NDF and ADF declined by 3.07%~39.72% (P < 0.01) and 17.80%~45.91% (P < 0.01), respectively. Effective rumen degradability of DM and OM, and a+b value of A. polytricha, F. velutipes and P. ferulae SMSs were significantly (P < 0.01) higher than those of cottonseed hull. Also effective rumen degradability of DM and OM, and a+b value of P. ostreatus SMSs were higher (P < 0.05) than those of cottonseed hull. Then effective rumen degradability of CP and a+b value of P. ostreatus, F. velutipes and P. ferulae SMSs were significantly (P < 0.01) higher than those of cottonseed hull. Effective rumen degradability of NDF and ADF of 4 SMSs increased by 76.72%~702.63% (P < 0.01) and 137.41%~575.31% (P < 0.01), respectively. In conclusion, nutritional value and effective rumen degradability of the 4 SMSs improved by mushroom cultivation on cottonseed hulls, which were also fit for use as feed for ruminants.