Objective: To explore the effect of Tripterygium polyglycoside (TP) associated with nicotinamide on the islet cell function, immune parameters and lipoperoxide (LPO) in adult patients with late-onset autoimmune diabetes mellitus (LADA). Methods: Thirty-six cases of LADA were randomly divided into three groups: TP group (n=12), treated with TP plus orally taken metformin; combined treatment group (n= 12), treated with TP combined with nicotinamide and metformin, and control group (n=12) treated with metformin alone. They were followed-up for 18 months. Results: (1) Compared with the control group after 9 months of treatment, postprandial plasma glucose and LPO in combined treatment group were decreased (P <0.05), and the postprandial C-peptide was higher (P<0.05). At the 18th month, the value of postprandial C-peptide in the TP and combined treatment group was higher than that in the control group. The slL-2R level of both TP and combined treatment groups were lowered (P<0.01); (2) Islet cell antibody (IC Objective: To explore the effect of Tripterygium polyglycoside (TP) associated with nicotinamide on the islet cell function, immune parameters and lipoperoxide (LPO) in adult patients with late-onset autoimmune diabetes mellitus (LADA). Methods: Thirty-six cases of LADA (n = 12), treated with TP combined with nicotinamide and metformin, and control group (n = 12) treated with TP plus orally taken metformin; They were followed-up for 18 months. Results: (1) Compared with the control group after 9 months of treatment, postprandial plasma glucose and LPO in combined treatment group were decreased (P <0.05), and the postprandial C -peptide was higher (P <0.05). At the 18th month, the value of postprandial C-peptide in the TP and combined treatment group was higher than that in the control group. The slL-2R level of both TP and combined treatment groups were lowered (P <0.01); (2) Isle t cell antibody (IC