In this study, Lactobacillus casei 16 was used to ferment soymilk. The effects of different fermentation time, fermentation temperature and refrigeration time on pH value, total phenol content, free amino acid content, and physical properties of L. casei 16 fermented soymilk were further investigated. The orthogonal experiment was further adopted to optimize the fermentation conditions of L. casei 16 fermented soymilk, with total phenol content and free amino acid content as indicators. Moreover, the antioxidant capacity of fermented soymilk after optimization was also investigated. The optimized conditions were found that L. casei 16 was inoculated into soymilk with concentration of 2%, fermented at 37 ℃ for 24 h, and then refrigerated at 4 ℃ for 6 h after fermentation. Under the control of these conditions, the total phenol content was 13.94 mg/100 mL, and the that of free amino acids was 1.33 mg/mL, with the consistency of solution of 2 192.32 g·s. The total reducing power and hydroxyl radical scavenging ability were 0.31 and 79.43%, respectively, significantly higher than those of unfermented soymilk and unoptimized groups (P＜0.05).