Objective To investigate the expression of T cell subsets in the spleen of BTBR T⁺Itpr3^tf autistic mouse at 4, 8, and 12 weeks of age, and to determine the optimal age for studying the relationship between immune abnormalities and autism in BTBR autistic mice. Methods It randomly selected 5~6 male BTBR mouse at 4 weeks, 8 weeks, and 12 weeks of age and C57BL / 6J mouse of the same gender at corresponding ages for the three-box social interaction test, the self-grooming test, and the marble-burying test; Single cell suspensions were prepared from the spleens of mouse at 8 and 12 weeks of age, and flow cytometry was used to detect 8 subsets of T cells (T_H 1, T_H 2, T_H 17, T_C1, T_C2, T_C17, T_FH , and T_reg). Results Compared with C57BL / 6J mouse of the same age, BTBR mouse at 4 weeks, 8 weeks, and 12 weeks of age showed a decrease in social time(P<0. 001), an increase in grooming time (P<0. 01,P<0. 001), and an increase in the number of marbles buried(P<0. 01,P<0. 001) in BTBR mouse at 8 weeks and 12 weeks of age. As well, the expression of T_H 1(P<0. 001), T_H 2(P<0. 01), T_C1(P<0. 05), T_C2(P<0. 001), and T_FH(P<0. 01)cells in 8-week-old BTBR mouse were significantly increased, while the expression of T_reg (P<0. 001)cells were significantly decreased; The expression of T_H 1(P<0. 01), T_H 2(P<0. 01), T_H 17(P<0. 05),T_C1(P<0. 01), T_C2(P<0. 001), T_C17(P<0. 01), and T_FH ( P<0. 001) increased in 12-week-old BTBR mouse,while the expression of Treg(P<0. 05) cells decreased. At different age stages (P<0. 050) the ratio of T_H 1 / T_reg and T_C1 / T_reg in 8-week-old BTBR mouse were significantly higher than those in 12 week old mouse, while the T_C17 / T_reg ratio decreased. Conclusions BTBR mouse at different developmental stages exhibit varying degrees of abnormal increase in T_eff / T_reg ratio. Based on result of behavioral test, it is recommended to use 8-week-old BTBR mice for research on autism and immune abnormalities.