Abstract: In order to screen more materials that could be used as the mattresses of microbial fermentation bed for pig breeding, by taking the hull/saw bran bedding and coconut bran bedding as the research objects, the differences of nutritional components, microbial content and volatile substances of different bedding materials after raising the nursery pigs for 12 months were analyzed. The results showed that raising the nursery pigs for 12 months, the two kinds of bedding materials had lower degree of maturity, and the contents of organic matter, humic acid, humic acid fraction, fulvic acid, total nitrogen and total potassium (K₂O) in the coconut bran bedding were higher than those in the hull/saw bran bedding. The content of culturable microorganisms in the coconut bran bedding was 0.15×10⁷ cfu·g^-1, which was significantly lower than that in the hull/saw bran bedding (3.60×10⁷ cfu·g^-1), and no salmonella was detected. There were few types and low contents of volatile substances (matching degree≥90) detected in the two bedding materials. Among them, there were two kinds of volatile substances in the coconut bran bedding, which were 1,4-dichlorobenzene (3.91%) and D-camphor (1.667%), respectively; and there were three kinds of volatile substances in the hull/saw bran bedding, which were 1,3-dichlorobenzene (3.65%), lumbar camphor (1.36%) and B-cedrene (0.66%), respectively. The two kinds of bedding materials could be used as the good raw materials of humic acid (NY/T1106-2010 ″water-soluble fertilizer containing humic acid″ or the raw materials of organic fertilizer (NY/T525-2021 ″standard of organic fertilizer″) after being used for 12 months.