Abstract: To comprehensively utilize stalk residue of Pleurotus ostreatus, improve its added value, and develop a production base material for edible fungus condiments, this study carried out the following work: Using the concentrated enzyme-hydrolyzed solution of stalk residue of Pleurotus ostreatus as raw material, glucose was added, and the Maillard reaction was applied to prepare the flavor base material. Single-factor experiments and orthogonal experiments were used to optimize Maillard reaction conditions, with sensory score, system pH and browning degree as evaluation indicators. Free amino acid content was determined in the concentrated solution and the Maillard reaction products (MRPs) prepared under the optimal reaction conditions, and the contribution of amino acids to taste was also analyzed. The characteristic flavor of MRPs was analyzed using a gas chromatography-mass spectrometry (GC-MS) instrument, and the antioxidant capacities of the concentrated enzyme-hydrolyzed solution and MRPs were compared. The results showed that the order of influence of the four single factors on the Maillard reaction was: initial pH > glucose addition amount > reaction temperature > reaction time. The optimal conditions for the Maillard reaction were: 7.0% glucose addition, initial pH 7.0, and reaction at 100 ℃ for 80 minutes. The prepared product was reddish-brown, with obvious umami taste and slight sweetness, and had a typical Pleurotus ostreatus aroma mixed with a roasted hazelnut scent. Seventeen free amino acids were detected in both the concentrated solution and MRPs, among which glutamic acid, serine, alanine, and tyrosine had relatively high contents. After the Maillard reaction, the content of bitter amino acids decreased; the content of umami amino acids (aspartic acid and glutamic acid) was 2.733 mg/g, accounting for 33.4% of the total free amino acid content. The taste activity values (TAV) of glutamic acid and alanine—both contributing significantly to taste—were 8.097 and 1.240, respectively, and the taste-active amino acid composition of MRPs was improved compared with that of the concentrated solution. A total of 42 volatile substances were detected and identified in MRPs, including 17 aldehydes, 10 ketones, 6 hydrocarbons, 5 alcohols, 3 heterocyclic compounds and 1 acid. The compounds with relatively high relative contents were heterocyclic compounds (44.93%) and aldehydes (33.07%). Relative odor activity value (ROAV) results show that 2,4-decadienal (ROAV=100), 2-pentylfuran (ROAV=50.29) and C₆~C₁₀ aliphatic aldehydes are the main aroma contributors of MRPs. Results of antioxidant experiments indicate that both the reducing power and DPPH free radical scavenging capacity (IC₅₀=0.86 mg/mL) of MRPs were significantly improved. This study established an effective method for the resource utilization of stalk residue of Pleurotus ostreatus, provided a new approach for condiment production, and had good market application prospects.