Abstract: Nonlinear optical switch based on two-dimensional material is the core device of Q-switched fiber laser. The concentration of two-dimensional material optical switch will directly affect its nonlinear optical absorption characteristics, thus change the time-domain characteristics of the pulse. Therefore, the influence of two-dimensional material concentration on Q-switched optical pulse was studied, and a saturable absorption optical switch based on Ti: Bi₂Te₃ with different concentrations was made through experiments. The influence of Ti: Bi₂Te₃ concentration on nonlinear optical absorption characteristics was analyzed, and the relationship among the modulation depth, pulse width, repetition frequency and single pulse energy of Q-switched optical pulse with different concentrations Bi₂Te₃ was obtained. Finally, the Ti:Bi₂Te₃ concentration was optimized for the resonator parameters. When the pump power is 71 mW, the central wavelength is 1 560 nm, the pulse width is 8 μs, the repetition frequency is 14.2 kHz, the average output power is 2.15 mW, and the corresponding single pulse energy is 151.4 nJ.