We theoretically investigate power-induced lasing state switching and bistability in a two-state quantum dot laser subject to optical injection. The simulated results show that, for a free-running two-state quantum dot laser operating at the ground state under low current, a power-induced lasing state switching between the ground state and the excited state can be achieved through introducing optical injection with a frequency (winj) close to the lasing frequency of excited state (wES). The injection power required for the state switching depends on the scanning route of injection power, i.e. there may exist state bistability for the injection power within a certain region. For forward scanning injection power, with the increase of frequency detuning (ΔΩ = winj – wES), the injection power required for the state switching shows a decreasing trend accompanied by slight fluctuations. However, for backward scanning injection power, the injection power required for the state switching exhibits obvious fluctuations with the increase of ΔΩ. The width of the hysteresis loop fluctuates with ΔΩ, and the fluctuation amplitude is increased with the increase of the injection current. Additionally, the influences of the inhomogeneous broadening factor and the electron escape rate on the bistability performances are analyzed.