Surface plasmon resonance (SPR) sensors based on quasi-bound states in the continuum (quasi-BICs) have demonstrated extensive applications across biomedical, environmental monitoring, and industrial production sectors owing to their exceptional quality factor (Q-factor) and remarkable optical tunability. However, current research mainly focuses on the mode analysis of quasi-BICs, and insufficient attention has been paid to the relationship between quasi-BICs and the intrinsic parameters in photonic sensors such as intensity sensitivity, noise-equivalent limit of detection (LOD), and Figure of Merit (FOM). In this paper, a high-Q quasi-BIC is introduced into a SPR sensor, and its influence on the sensing performance, including intensity sensitivity, LOD and FOM, is discussed in detail. The analysis show that compared with the traditional SPR mode, the quasi-BIC with an ultra-high and tunable Q-factor not only improves the intensity sensitivity of the device but also reduces the noise and optimizes its LOD and FOM. On this basis, we design a high-performance temperature sensor using polydimethylsiloxane (PDMS) thermo-sensitive material. The simulation results show that the temperature sensitivity of the device is as high as −0.33 nm/°C with the advantage of low noise. This theoretical analysis will provide guidance for the practical application of quasi-BICs in the field of sensing.