The polarization bistability (PB) features in a 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL) subject to variable polarization optical injection (VPOI) are experimentally investigated. We have investigated the influence of polarization angle θ, of optical injection on PBs induced by scanning the power (power-induced PB) and the frequency of injected light (frequency-induced PB) along with different routes. The experimental results show that, for the fixed frequency of the injection laser and by scanning the injection power within a certain region, there exists a determined range of θ, in which power-induced PB in the 1550 nm-VCSEL subject to VPOI can be observed. For VPOI with θ, located within the determined range, the power-induced PB possesses larger hysteresis width, as compared with orthogonally polarized optical injection. The hysteresis width will be larger for a smaller value of θ,. Under the condition of fixed injection power and continuously varying the frequency of the injection laser, two frequency-induced hysteresis cycles can be observed, of which one is located at negative frequency detuning, and the other is located at positive frequency detuning. The variations of the two hysteresis width with θ, exhibit different trends. Also, when the bias current of the 1550 nm-VCSEL increases, the hysteresis width can be further broadened for the power-induced PB, and the broadening effect is relatively weak for the frequency-induced PB.