Abstract: The existence of multiple states characterized by different large-scale flow structures or different statistical properties in a turbulent flow has attracted lots of research interests. In this paper, we present an experimental study of multiple states and heat transport in turbulent thermal convection. The experiment was carried out in an annulus Rayleigh-Benard turbulence system with a Rayleigh number (Ra) range of 2×10⁸ ≤Ra ≤ 2.9×10⁹ and at a fixed Prandtl number of Pr = 5.4. Consistent with the discovery by Xie, Ding & Xia, (Phys Rev Lett, 120, 214501, 2018.), we show in a wider range of Ra that the large-scale flow bifurcates from a high-heat-transport efficiency state to a low-heat-transport efficiency state. Direct measurements of the flow structure using particle image velocimetry reveal that the large-scale flow in the high-heat-transport state shows a quadrupole structure, and the low-heat-transport state shows a dipole structure. In addition, it is found that the third and fourth flow modes are more efficient in heat transport when compared with the dipole and the quadrupole modes. This observation provides another evidence that the higher the symmetry of the flow, the higher the heat transport efficiency. When the large-scale flow is dominated by the dipole mode, it is showed that there is a preferred orientation which acts as a potential well. Further analysis shows that when the large-scale flow is trapped in this preferred orientation, its random azimuthal meandering is suppressed dramatically with increasing Ra. The annulus cell used in the present study will unavoidably introduce the spatial confinement effect. It is found that this spatial confinement not only changes the structure of the large-scale flow but also alters its dynamics. Whether spatial confinement leading to an enhanced or a reduced heat transport efficiency depends on the resulting large-scale flow modes, i.e., when spatial confinement results in higher order flow modes, the heat transport efficiency is enhanced, otherwise reduced.