This study aimed to analyze crude protein, amino acid and bioactive changes in Phellinus linteus HN00K9 cultured oat. The crude protein content of P. linteus cultured oat (PCO) was 12.9%, which was higher than that of uncultured oats (UCO) as control at 11.26%. The total free amino acid contents of PCO and UCO were 11,4 mg/100 g and 9,686.205 mg/100 g, respectively. Glutamic acid accounted for 21% of the total amino acids of PCO, and the histidine content was increased by more than 51% in PCO compared to UCO. The total polyphenol content of PCO was 275 mg GAE/g, which was more than twice that of UCO (135 mg). The DPPH radical scavenging activity was 15.5% in PCO, which was more than five times that of UCO (3.5%). The β-glucan content of PCO was 12.5 g/100 g, which was more than five times that of UCO (3.2 g/100 g). Therefore, it is believed that PCO can be utilized as a material for various functional foods.