Purpose: To explore the possible mechanism of Maillard reaction (MR) involvement in the steam processing of Panax notoginseng (PN) root. Methods: PN root was soaked in water for 24 h and then steamed at 100 °C using an autoclave for 1, 2, 3, 4, 5 and 6 h, respectively. Several indicators associated with MR during steam processing were measured. The pH and absorbance at 420 nm (A420) of samples were measured using a pH meter and an ultraviolet-visible spectrophotometer, respectively. The contents of 5-hydroxy-methyl-furfural (5-HMF) and sugars were determined by high performance liquid chromatography (HPLC) while amino acids were evaluated using an automatic amino acid analyzer. Results: During PN root steam processing (0-6 h), pH value gradually decreased from 6.35 ± 0.02 to 5.88 ± 0.03 while A420 value gradually increased from 0.23 ± 0.01 to 0.44 ± 0.02. The levels of reducing sugars (maltose and glucose) and amino acids (aspartic acid, glutamate, cysteine, lysine and arginine) in PN root decreased after steaming for 6 h. However, the content of 5-HMF in PN root increased with increase in steaming time. Conclusion: The results indicate that MR occurs during steam processing of PN root, and the reaction mechanism might be closely related to the reaction between the reducing sugars and amino acids.