The mycelium materials incubating Pleurotus ostreatus fungi based on different substrate compositions were developed, the main components of which were poplar sawdust and cottonseed hull in different proportions. The hyphae on the surface of the samples become dense from appearance due to the addition of cottonseed hull. The Fourier Transforms Infrared analysis revealed that the cellulose, hemicellulose and lignin in substrates of all samples were degraded in different degrees owing to utilization by hyphae growth. The morphology and mechanical properties of the mycelial materials changed as the substrate compositions varied. The difference of properties among all mycelium materials was mainly attributed to the growth of mycelium and different substrate compositions. And the mycelium material (the ratio of poplar sawdust to cottonseed hull was 1) exhibited highest strength and lowest compression set, indicating that its size recovery capability was best. In comparison, the substrate of this material was more favorable to the growth of the mycelium and it showed optimal comprehensive performance among all samples. The mycelium material showed good potentiality for packaging application.